There are 4 Hogwarts Houses: Gryffindor, Hufflepuff, Ravenclaw, and Slytherin.
"You might belong in Gryffindor,
Where dwell the brave at heart,
Their daring, nerve, and chivalry
Set Gryffindors apart."
- Hogwarts Sorting Hat
To be chosen as a Hufflepuff, you must be:
Unafraid of toil,
Just and loyal,
Patient,
Honest,
Sweet,
and a Hard Worker.
Qualities of a Ravenclaw:
Wise.
Sharp mind.
Wit and Learning.
Fair, Clever, and Intelligent.
"Shrewd Slytherin, from fen..."
"...And power-hungry Slytherin Loved those of great ambition..."
"...For instance, Slytherin took only pure-blood wizards Of great cunning, just like him..."
- Hogwarts Sorting Hat
There are many characters in all 8 Harry Potter books. I'll start with Harry, Hermione, and Ron, and then work my way through the rest, in the order they are mentioned in the books.
At the age of eleven, Harry James Potter was small and skinny.
He had a thin face, knobbly knees, black hair, and bright green eyes. He wore round glasses, and had a scar on his forehead that was shaped like a bolt of lightning. It was also at the age eleven that Harry found out he was a wizard. And not just a wizard, but a famous one.
At the age of one year old, Harry had somehow survived a curse from the greatest Dark sorcerer of all time, Lord Voldemort. Harry's parents had died in Voldemorts attack, but Harry had escaped with his lightning scar and somehow Voldemort's powers had been destroyed the instant he had failed to kill Harry. - Page 4 of Chamber of Secrets
Hermione Jean Granger is a bushy-haired, somewhat bossy girl who is what some people might call "Muggle-born."
Ronald Bilius Weasley is a red-haired and freckled wizard. He lives with 5 brothers (and one sister) and is the youngest brother out of all of them.
Vernon Dursley was a big, beefy man with hardly any neck, although he did have a very large mustache. Vernon was the director of a firm called Grunnings, which made drills.
Petunia Dursley was thin and blonde and had nearly twice the usual amount of neck, which came in very useful as she spent much of her time craning over garden fences, spying on the neighbors.
Dudley Dursley had a large pink face, not much neck, small, watery blue eyes and thick blonde hair that lay smoothly on his thick, fat head.
Tom Marvolo Riddle is not an innocent little school boy. As Harry learns in Book 2 Of the Harry Potter Series, Tom is Lord Voldemort, more commonly known as "You-Know-Who." At the age of 16, Tom was a tall, black-haired boy. When he grew older, however, Tom changed into a man, whiter than a skull, with wide, livid scarlet eyes, and a nose that was flat as a snake's, with slits for nostrils.
Jim MucGuffin is a weatherman on the Muggle News.
Ted is also a weatherman on the Muggle News.
Albus Percival Wulfric Brian Dumbledore is a tall, thin, and very old man, judging by the silver of his hair and beard, which were both long enough to tuck into his belt. His eyes are light, bright, and sparkling behind half-moon spectacles and his nose is very long and crooked, as though it had been broken many times.
Minerva McGonagall is a Professor at Hogwarts. She teaches Transfiguration. She is a rather severe-looking woman who wears square glasses, and her black hair is always drawn into a tight bun.
Dedalus Diggle is a little man in a top hat.
Poppy Pomfrey is the nurse at Hogwarts. She is a very nice woman, but strict.
Lily Potter (left) was a very pretty woman. She has dark red hair, and bright green eyes. She is the mother of Harry Potter. James Potter (right) is Harry Potter's father. He was a tall, thin, black-haired man who wore glasses and his hair was very untidy.
Rubeus Hagrid is the Keeper of Keys and Grounds at Hogwarts. His mom was a giant and his dad was a human. This makes Hagrid half-giant. he has a long, shaggy mane of hair and a wild, tangled beard, with black beetle eyes.
Sirius Black is an Animangus. He can turn into a black-haired dog, which can be mistaken as a Grim. He has long black hair and very yellow teeth. He is Harry Potter's godfather.
Marjorie (Marge) Dudley is Vernon's sister. She resembles Vernon a lot. She is large, beefy, and purple faced. She even has a mustache. She owns an old and evil-tempered bulldog, who likes to chase Harry up trees.
Arabella Doreen Figg is Harry's neighbor. She is a Squib. She usually babysits Harry on Dudley's birthdays.
Yvonne is Petunia's friend.
Piers Polkiss (from left to right behind Dudley: he's #3) was a scrawny boy with a face like a rat. He is Dudley's friend. Dennis (#1), Malcolm (#4), and Gordon (#2) are all big and stupid. They are also Dudley's friends.
Cornelius Oswald Fudge was one of the Ministers of Magic. He has rumpled gray hair and an anxious expression, and wear a strange mixture of clothes: a pinstriped suit, a scarlet tie, a long black coat, and pointed purple boots.
Tom is the bartender at the Leaky Cauldron. He is quite bald and looks like a toothless walnut. The producers of the Harry Potter movies switched the actors for this character, so there are two different ones.
Doris Crockford is one of the ones who met Harry Potter in the Leaky Cauldron in the very first book.
Professor Quirrell was the Defense Against the Dark Arts teacher in Book 1 of the Harry Potter Series. He was a pale young man, who is frightened of almost everything, including his job.
Griphook is a goblin who works at Gringotts Bank.
Madam Malkin runs a shop called Madam Malkin's Robes for All Occasions. She was a squat, smiling witch dressed in all muave.
Professor Vindictus Viridian is the author of Curses and Countercurses (Bewitch Your Friends and Befuddle Your Enemies with the Lastest Revenges: Hair Loss, Jelly-Legs, Tongue-Tying, and Much, Much More).
Ollivander is the owner of his very own wand shop. He is an old man, with wide, pale eyes.
Ginny Weasley is the youngest member of the Weasley family. She is a small, red-haired girl.
Fred Weasley is George Weasley's twin. So, of course, both of them have red hair. Fred and George Weasley are somewhat the "class clowns" at Hogwarts.
Molly Weasley is a plump woman and the mother of 7 children. She is also the wife of Arthur Weasley.
Percy Ignatius Weasley is the third oldest brother in the Weasley family. He turns out to be a snobby git.
Bill Weasley is the oldest brother in the Weasley family. He works at Gringotts Bank.
Charlie Weasley is the second oldest brother in the Weasley family. He works in Romania with dragons.
Agrippa is a wizard on a Chocolate Frog Card.
Ptolemy is a wizard on a Chocolate Frog Card.
Morgana is a wizard on a Chocolate Frog Card.
Hengist of Woodcroft is a wizard on a Chocolate Frog Card.
Alberic Grunnion is a wizard on a Chocolate Frog Card.
Circe is a wizard on a Chocolate Frog Card.
Paracelsus is a wizard on a Chocolate Frog Card.
Merlin is a wizard on a Chocolate Frog Card.
Cliodna is a wizard on a Chocolate Frog Card.