Factual error: When Wood is telling Harry the rules of Quidditch he says that if you catch the Snitch the game is over, which is true but then he also says that which ever seeker catches the snitch, their team wins, but that isn't true. Granted that the 150 extra points probably would give you the winning lead, but as JKR pointed out in the 4th book at the Quidditch World Cup, you can catch the Snitch but lose the match. And you'd think explaining the rules to a first-timer you would want to get it right.
Factual error: The Hogwarts Express leaves from platform nine and three-quarters, between platforms nine and ten at King's Cross station, London. The platforms shown in the film as nine and ten are, in fact, four and five (the only platforms that have a wall between them as shown in the film). The real platforms nine and ten are in a separate part of the real station. In addition, when Hagrid and Harry are on the footbridge, they are walking towards platform one, away from both the real platforms 9 & 10 and the film's platforms 9 & 10. No wonder Harry feels lost when Hagrid leaves him to find the train on his own!
Factual error: When Hagrid visits the Dursley family in the hut on the rock, Hagrid grabs and bends the shotgun barrel while it is still being held by Mr. Dursley. This is impossible. The gun is made of strong metal, and when Hagrid grabs it, it starts bending, while still in Dursley's grip. Seeing as how Hagrid (the half Giant) is very strong, he should either knock Dursley to the floor or pull the gun straight out of his hands (and maybe his arms with it), if Dursley were to really keep hold of the gun as it is bending. Mr. Dursley must have one strong grip.