Saying the magic words properly is very important, too - never forget Wizard Baruffio, who said "s" instead of "f" and found himself on the floor with a buffalo on his chest.
Filius Flitwick in Harry Potter and the Philosopher's StoneFlitwick: "There you are! We've been looking everywhere for you two. Now, names?"
Harry: "Professor Flitwick, you've known me for five years."
Flitwick: "No exceptions, Potter!"
Thank you so much, Professor! I could have got rid of the sparklers myself, of course, but I wasn't sure whether I had the authority.
Filius Flitwick in Harry Potter and the Order of the Phoenix, to Dolores UmbridgeProfessor Flitwick took the register, and when he reached Harry's name he gave an excited squeak and toppled out of sight.
Filius Flitwick in Harry Potter and the Philosopher's StoneAs long as the Secret-Keeper refused to speak, You-Know-Who could search the village where Lily and James were staying for years and never find them, not even if he had his nose pressed against their sitting room window!
Filius Flitwick in Harry Potter and the Prisoner of AzkabanThe diadem of Ravenclaw? A little extra wisdom never goes amiss Potter, but I hardly think it would be much use in this situation.
Filius Flitwick in Harry Potter and the Deathly HallowsNow, now, boys. A little less talk, a little more action... Let me see you try.
Filius Flitwick in Harry Potter and the Half-Blood PrinceHogwarts should be Dumbledore's final resting place.
HogwartsFilius Flitwick in Harry Potter and the Half-Blood PrinceYou'll do no more murder at Hogwarts!
Filius Flitwick in Harry Potter and the Deathly Hallows, to Severus SnapeYou realize, of course, that nothing we do will be able to keep out You-Know-Who indefinitely?
Filius Flitwick in Harry Potter and the Deathly HallowsDon't forget the nice wrist movement we've been practicing, the Swish and Flick!
Filius Flitwick in Harry Potter and the Philosopher's StoneQuills down, please! That means you too, Stebbins! Please remain seated while I collect your parchment! Accio!
Filius Flitwick in Harry Potter and the Order of the Phoenix