1)Say "I told you so..." as many times as you can, even if it makes your best friends feel awful
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 to look like a true know-it-all
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.
9)Condone it wholeheartedly when your best friend acts like a jerk to a girl he obviously used/took advantage of
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
Have I missed anything? I'm sure Hermione has so many things to teach us!