Corrected entry: This must always be a risk when working with child actors and filming out of sequence, but Daniel Radcliffe's voice obviously started to break during filming. It was most noticeable during the scene in the forest when his voice went from high to low to high again (and again, and again...)
Corrected entry: After the Quidditch Match Hagrid says something like 'That's strictly between Dumbledore and Nicolas Flamel.' When he finishes Harry says 'Nicolas Flamel?' Watch Ron. He is mouthing Harry's lines.
Corrected entry: During the final chess game when the Queen is moving into position to smash Rons knight, they cut back and forth from the Queen to Ron. During one cut, the queen figure has its fingers laced and sticking out; in the next shot, one hand is a fist being covered by the other hand. Then it cuts back to outstretched laced fingers again.
Correction: The other hand configuration belongs to the King.
Corrected entry: When Quirrell reports that there is a troll in the dungeon then faints he is laying one direction, but a few seconds later from a different shot he is laying the opposite direction.
Correction: When Quirrell falls, he falls face down with his head towards Professor Dumbledore, and his feet towards the door. When the children run out, we again see Quirell, and he is facing the same way.
Corrected entry: In the scene in the Great Hall where Ron is looking at his Chocolate Frogs cards, Harry picks one up. It's suppose to be Dumbledore's card, but in several shots you see where Dumbledore's picture should be. Instead, all you see is the green screen attached to the cards.
Correction: Dumbledore's picture was a simple holographic foil image; the same kind you'd see on any credit card. There was no green screen effect needed for this. What you're seeing is just the way the light plays off the foil when viewed from an extreme angle.
Correction: Only natural - voices don't break evenly. I think they filmed it mostly in sequence to avoid any major shifts.