Er, I meant to say Half-Blood Prince, silly me! Anyway,
1)When you don't like the commentary, attack the sports commentator
2)If you don't want some one to qualify for your favourite sports team, sabotage the tryouts
3)If your best friend is dating a paramour who isn't you, comission wildlife to leave him/her wounded
4)Smirk often to show just how smug you are, and how stupid your friends are
5)Give un-asked for advice as often as humanly possible
6)If anyone around you is out-performing you, acuse them of cheating or doing something unethical
7)Arguing=Love in the Harry Potter universe, and engaging in it daily is a sign of twooo lurve
8)You can get away with crying over stupid things(jealousy, losing an argument) if you're JKR's Mary-Sue, but not if you're a character JKR hates, because you'll be labelled a human hosepipe then.
9)Condone it wholeheartedly when your best friend acts like a jerk to a girl he obviously used/took advantage of, then condemn him for not noticing you sooner
10)Memorize as much book-knowledge as possible so you can recite it verbatim in class, thereby sounding like a know-it-all, or a walking tome
11)Life's too short not to have shallow romances, so fall in love as quickly as you can with the next available thing with a pulse.
12)Berate people behind their backs, then chide those around you for doing the very same thing
13) Your IQ can drop 50-80 points without warning
14) Your personality can change so much in a matter of months, to the point where you are almost perceived as a different person entirely
15) Pretending to be asleep every time a girl, who you've incidentally used like toilet tissue and then discarded, turns up to see how you are, will fool them thoroughly, and is an acceptable course of action.