• There are 7 books in the Harry Potter series
• There are 7 years of studies at Hogwarts
• Harry's birthday is in July which is the 7th month of the year
• The Weasley family has 7 children
• The Alohomora spell can be found in the Standard Books of Spells chapter 7
• There are 7 Quidditch players in a team
• There are 142 stairs at Hogwarts which adds to 7 (1+4+2=7)
• Gryffindor Tower is located on the 7th floor
• Nicholas Flamel and his wife have 7 years age difference
• Hogwarts students have to buy all 7 of Lockhart's books
• Flitwick's office (where Sirius is locked in the 3rd book) is located on the 7th floor
• There are 7 locks in Moody's trunk
• Moody was locked in the 7th lock of his trunk
• In the American version of PoA beginning Chapter 15, is an illustration of Hagrid's letter to Hermione in regards to Buckbeak's trial which shows 7 teardrops.
• In OotP, during Harry's trial, Dumbledore states '...clause seven of the Decree [for the Reasonable Restriction of Underage Sorcery] states that magic may be used before Muggles in exceptional circumstances...'
• in PoA, when Snape is filling in for Professor Lupin, he instructs the class to turn to page 394. 3+9+4 = 16: 1+6 = 7. (also see 'The Number 12' regarding this number)
• There are 7 animagi registered with the Improper Use of Magic Office

Sorcerer's/Philosopher's Stone

• Dumbledore uses his Put-Outer to extinguish the 12 street lamps on Privet Drive.
• Dumbledore's watch has 12 hands.
• The milkman delivers two dozen letter-filled eggs to the Dursley's.
• On Friday, 12 letters arrive for Harry.
• Hagrid is described as being at least twice the height of a normal man. If a normal man is around 6 feet tall, that would make Hagrid approximately 12 feet tall.
• Platform 9 3/4 - 9 is 3/4 of 12
• The troll Quirrell let in on Halloween was 12 feet tall.
• During the flying lesson, Neville originally rises to 12 feet.
• The Wizards Duel with Draco was supposed to happen at midnight.
• At the first Quidditch Match, Neville tells Draco he's worth 12 of him.
• There are 12 Christmas trees in the Great Hall.
• Dumbledore is famous for discovering the 12 uses of Dragon's blood.
• At exactly 12:00 AM Harry turns 11, and Hagrid bangs on the door.
• Shortly before the trio leaves to go through the trapdoor, Hermione says that she won't get kicked out because she got 112 percent on Flitwick's exam.
• Harry hears Quirrell sobbing and giving in to someone in a classrom. After Quirrell leaves the room, Harry says he would bet 12 Sorcerer's Stones that the other person in the room was Snape.
• Gryffindor was "in fourth place, with three hundred and twelve points".
• JKR said in an online chat that her favorite chapter out of all the books was Chapter 12, Book 1 (The Mirror of Erised)

Chamber of Secrets

• Harry turns 12 years old.
• After Dobby drops the pudding on the kitchen floor, Harry receives an owl from the Ministry saying that a Hover Charm was used at 12 minutes past 9.
• When Draco is complaining about Harry, Lucius cuts him off and says he's heard this a dozen times already.
• There are 12 school governers.
• Lockhart says there are 12 dwarf cupids roaming around the school delivering Valentines.
• Lockhart says that in Chapter 12 of his book, Wandering with Werewolves, he divulges that his ideal birthday gift is to have peace among all creatures.
• We learn that Bill and Percy both got 12 O.W.L.s.
• Ron says he wrote to Harry at least 12 times over the Summer.

Prisoner of Azkaban

• Aunt Marge has 12 bulldogs.
• Sirius escaped from Azkaban after being imprisoned for 12 years.
• To get his mind off of Aunt Marge's insults, Harry tries to remember page 12 of his book: "A Charm to Cure Reluctant Reverses."
• Harry's Nimbus 2000 was smashed into a dozen pieces.
• Fudge says Black murdered 12 muggles and 1 wizard with a single curse. We should note here that Pettigrew actually DID murder 12 muggles in total. Thanks to Joel for pointing that out!
• At The Leaky Cauldron, Ron and Percy stay in room #12.
• Buckbeak's wingspan is said to be 12 meters long.
• Snape, substituting for Lupin's Dark Arts class, tells the students to turn to page 394 - to play with those numbers we get: 3 + 9 = 12, 3 x 4 = 12, 9 is 3/4 of 12. (also see 'References to the Number 7' regarding this number)
• Ron tells everyone when he woke, Sirius was standing over him with a 12 inch knife.
• Sirius tells Harry he got him the Firebolt because of 12 birthdays without presents.
• At the Christmas feast, Trelawney counts 12 people at the table and refuses to sit down because she would be thirteen.
• McGonagall isn't happy when Harry asks about the status of his broom for the 12th time.
• Sirius tells Lupin to hurry up with the explanation since he's been waiting 12 years to get back at Pettigrew.

Goblet of Fire

• Frank Bryce estimates Nagini to be 12 feet long.
• While Percy is lamenting about Rita Skeeter's complaints that they should be stamping out vampires instead of quibbling about cauldron thickness, he says: "As if it wasn't specifically stated in chapter 12 of the Guidelines for the Treatment of Non-Wizard Part-Humans--"
• "By 12 o'clock the next day, Harry's school trunk was packed with his school things and all his most prized possessions."
• The basilisk fang from Harry's second year is described as being 12 inches long.
• At the Quidditch World Cup, the Bulgarians insisted on having 12 more seats in the Top Box.
• Crouch's grandfather used to have a magic carpet that could seat 12.
• The letter Harry sends Sirius after the first task is so heavy that when Harry tosses Pigwidgeon out the window with it, he plummets 12 feet before recovering.
• The Weasley's grandfather clock shows where each family member might be (such as "work," "traveling," etc.). In the position where the number twelve would be it states "mortal peril."
• As Harry is about to enter the Common Room after being picked as School Champion, a dozen hands pull him inside.
• In the Great Hall at the Yule Ball, instead of the usual four house tables there are 12 smaller tables.
• "Harry thought of Sirius, and the tight, tense knot in his chest seemed to ease slightly. He would be speaking to him in just over 12 hours."
• Hagrid tells Harry to meet him at midnight, and to bring that cloak with him.
• Sirius tells Harry he would need half a dozen wizards at a time to overcome a dragon.
• Harry, Ron and Hermione bring Sirius a dozen pieces of chicken.
• While Harry and Ron are making up false predictions for Divination, one of their prediction is that Harry will be stabbed in the back by someone he thought was a friend because Venus is in the 12th house.
• We learn that Dumbledore has been Hagrid's guardian since he was 12 years old when his dad died.
• Mundungus Fletcher put in a claim for a 12-bedroom tent with en-suite Jacuzzi.
• Cedric's wand is 12 inches long.
• Prof. Binns drones on about the goblin rebellions of 1612.
• 12 Dumstrang students arrive for the Triwizard Tournament.
• During the final task, the spider drops Harry 12 feet.
• Before Harry leaves to get Dumbledore, Crouch tells him that his son Crouch Jr. got 12 O.W.L.s.

Order of the Phoenix

• On the American cover there are 12 candles in the foreground.
• The headquarters of the Order of the Phoenix is located at number 12 Grimmauld Place.
• Harry had barely run a dozen steps when he reached Dudley and the dementor.
• Harry thinks it's "galling" to be told not to be rash by someone who had spent 12 years in Azkaban.
• Harry's disciplinary hearing with the Ministry is on the 12th of August.
• Sirius explains to Harry that Voldemort is not going to go up against the Ministry with a dozen death eaters.
• While Bill is asking Harry if he's alright, he's gathering up 12 scrolls at once.
• Roughly half a dozen of the Wizengamot vote in favor of conviction.
• One of Snape's homework assignments is 12 inches of parchment on the properties of moonstone and it's uses in potion-making.
• When Hermione is talking to Harry and Ron in the Great Hall, she glances around and sees a half a dozen empty seats around them.
• During Harry's detention with Umbridge, he glances out the window to the Quidditch Pitch and sees half a dozen black figures.
• At midnight, Harry is in the common room when he starts drifting off and almost gets to the door before he's awakened by Dobby.
• Harry sees Dobby picking up a half a dozen hats that Hermione left.
• Before Harry first enters Dumbledore's office after seeing the snake bite Mr. Weasley, Harry thinks it sounds like Dumbledore is entertaining at least a dozen people.
• When the Weasley kids are at Grimmauld Place worrying about their dad, Sirius summons a half a dozen butterbeers.
• "He was exhausted, he was confused beyond measure, he had experienced terror, relief, and then terror again in the last 12 hours, and still Dumbledore did not want to talk to him."
• Kingsley asks Mr. Weasley for as much information as possible on flying muggle vehicle sightings in the past 12 months.
• When they meet Lockhart in St. Mungo's, he says: "Well, how about those autographs then? Shall we make it a round dozen?"
• Harry is grumpy about having to go back to Hogwarts and place himself under the tyranny of Dolores Umbridge, who had no doubt managed to force through another dozen decrees in their absence.
• Harry makes a mental note how much more difficult it is to extend his arm 12 inches and touch Cho's hand than to snatch a speeding Snitch from midair.
• Hermione tells Harry to meet her at 12 o'clock in The Three Broomsticks during Harry's date with Cho.
• After the article in The Quibbler is published, Trelawney breaks out in tears during one of her classes and exclaims that Harry would not suffer an early death after all, but would live to a ripe old age, become Minister of Magic, and have 12 children.
• When James disarms Snape, his wand flies 12 feet in the air.
• Harry says he wasn't the sole witness to Voldemort's rebirth, and that there were a dozen-odd death eaters there too.
• There are a dozen doors in the circular room in the Department of Mysteries.
• When the trio are spread out in the shade of the beech tree near the lake, Ron talks them through his first save of the match for what felt like the dozenth time.
• In the Care of Magical Creatures O.W.L. the fifth years have to correctly identify a knarl hidden among a dozen hedgehogs.
• Ron reminds Harry that Hermione got 112% on her Charms exam last year.
• Ravenclaw sixth year Eddie Carmichael offers Ron and Harry a whole pint of Baruffio's Brain Elixir for 12 galleons.
• Harry pulls Ron's arm over his shoulder, just as he had done with Dudley months ago, and thinks they have a 1-in-12 chance of getting it right this time.
• There are a dozen death eaters in the Department of Mysteries.
• After Fudge sees Voldemort disapparate in the Ministry Atrium, Dumbledore tells him it's time he listened to sense, and he's been chasing the wrong man for 12 months.
• Dumbledore pulls out his watch with 12 hands and tells Fudge he may have a half-an-hour of his time.
• Fred and George's joke shop is at 93 Diagon Alley. 9 + 3 is 12.

1. Sorcerer's Stone - Professor Snape threatens Professor Quirrell, who we think is a decent man for resisting Snape. We soon discover that Professor Quirrell has joined with Lord Voldemort.
   
   
2. Chamber of Secrets - We learn about T.M. Riddle, which stands for Tom Marvolo Riddle, and is an anagram for I Am Lord Voldemort. We thought at first that Tom was a good person because he led us to believe that he had captured Hagrid with the creature from the Chamber of Secrets.
   
   
3. Prisoner of Azkaban - Wormtail, or Peter Pettigrew, fakes his death by hiding, making everyone believe that he had been eaten by Hermione's cat, Crookshanks. Of course, he's a rat, so how could we have thought there could possibly be anything wrong with him?
   
   
4. Goblet of Fire - 'Mad Eye' Moody, or at least, who we think is 'Mad Eye' Moody, makes his appearance, and turns Draco Malfoy into a white ferret, leading everyone to believe that he's a cool guy. A little Veritaserum, and short supply of Polyjuice Potion help reveal the truth!
   
   
5. Order of the Phoenix - Harry has detention with Dolores Jane Umbridge, and at no point during the book could anyone have thought that she was even remotely close to being a nice, caring, or loving person.
6.  Half-blood Prince - This rule does not apply to Chapter 13 in Half-Blood Princ, which is called The Secret Riddle. However Lord Voldermort does make an appearance in a memory that Dumbledore shows him. But does that count?
   
   

• His blue eyes were light, bright, and sparkling behind half-moon spectacles and his nose was very long and crooked, as though it had been broken at least twice. This man's name was Albus Dumbledore.
• Harry unwrapped his Chocolate Frog and picked up the card. It showed a man's face. He wore half-moon glasses, had a long, crooked nose, and flowing silver hair, beard, and mustache. Underneath the picture was the name Albus Dumbledore.
• Harry's whole body went numb. Dumbledore was looking unusually grave. He stared down his very crooked nose at them, and Harry suddenly found himself wishing he and Ron were still being beaten up by the Whomping Willow.
• The tip of Dumbledore's long, crooked nose was barely an inch from Mrs. Norris's fur. He was looking at her closely through his half-moon spectacles, his long fingers gently prodding and poking.
• Dumbledore took the diary from Harry and peered keenly down his long, crooked nose at its burnt and soggy pages.
• Professor Dumbledore, though very old, always gave an impression of great energy. He had several feet of long silver hair and beard, half-moon spectacles, and an extremely crooked nose.
• He amused himself for a moment, picturing Dumbledore, with his long silver beard, full length wizard's robes, and pointed hat, stretched out on a beach somewhere, rubbing suntan lotion onto his long crooked nose.
• Dumbledore made a small noise of dissent through his long, crooked nose.
• "And then, the boy would return to Hogwarts, where he is under the crooked nose of that Muggle-loving fool from morning until night. So how could I take him?"

• "Fifty points each," said Professor McGonagall, breathing heavily through her long, pointed nose.

• The creature slipped off the bed and bowed so low that the end of its long, thin nose touched the carpet. Harry noticed that it was wearing what looked like an old pillowcase, with rips for arm-and-leg holes.
• The house-elf's goggling tennis ball eyes were peering at Harry through the darkness. A single tear was running down his long, pointed nose.

• The tiny creature looked up and stretched its fingers, revealing enormous brown eyes and a nose the exact size and shape of a large tomato. It wasn't Dobby - it was, however, unmistakably a house-elf, as Harry's friend Dobby had been. Harry had set Dobby free from his old owners, the Malfoy family.

• [His face] looked as though it had been carved out of weathered wood by someone who had only the vaguest idea of what human faces are supposed to look like, and was none too skilled with a chisel. Every inch of skin seemed to be scarred. The mouth looked like a diagonal gash, and a large chunk of the nose was missing.

• Professor Quirrell, in his absurd turban, was talking to a teacher with greasy black hair, a hooked nose, and sallow skin.
• "Mr. Moony presents his compliments to Professor Snape, and begs him to keep his abnormally large nose out of other peoples' business."
• Harry spun around. There, his black robes rippling in a cold breeze, stood Severus Snape. He was a thin man with sallow skin, a hooked nose, and greasy, shoulder-length black hair, and at this moment, he was smiling in a way that told Harry he and Ron were in very deep trouble.
• Snape approached their table, stared down his hooked nose at the roots, then gave Ron an unpleasant smile from beneath his long, greasy black hair.
• On Professor Sinistra's other side was the sallow-faced, hook-nosed, greasy-haired Potions master, Snape - Harry's least favorite person at Hogwarts.
• Harry's loathing of Snape was matched only by Snape's hatred of him, a hatred which had, if possible, intensified last year, when Harry had helped Sirius escape right under Snape's overlarge nose - Snape and Sirius had been enemies since their own school days.
• "Please, sir, I'm supposed to take Harry Potter upstairs." Snape stared down his hooked nose at Colin, whose smile faded from his eager face.

• And so he tried to imagine his other best friend, Ron Weasley's, reaction, and in a moment, Ron's red hair and long-nosed, freckled face seemed to swim before Harry, wearing a bemused expression.

• Viktor Krum was thin, dark, and sallow-skinned, with a large curved nose and thick black eyebrows. He looked like an overgrown bird of prey. It was hard to believe he was only eighteen.
• Karkaroff beckoned forward one of his students. As the boy passed, Harry caught a glimpse of a prominent curved nose and thick black eyebrows. He didn't need the punch on the arm Ron gave him, or the hiss in his ear, to recognize that profile.
• Cedric and his parents were just inside the door. Viktor Krum was over in a corner, conversing with his dark-haired mother and father in rapid Bulgarian. He had inherited his father's hooked nose.

• Then there was the fact that Cedric looked the part of a champion so much more than he did. Exceptionally handsome, with his straight nose, dark hair, and gray eyes, it was hard to say who was receiving more admiration these days, Cedric or Viktor Krum.