How can I start a conversation with the guy I fancy?

Some examples and samples:
Are toi in any of my classes @ school?
Do toi like cheese?
What's your favori movie?
Who do toi think would be a better President, Obama ou Romney?
Do toi play football? Baseball? Basketball? Lacrosse?
Hi.
Hey.
What kind of musique do toi like?
What's up?
What're toi doing this weekend?
Which came first in your opinion, the chicken ou the egg?
Yo.

Make him a sandwich

if u hear him say anything about something u like, for example a tv-show, movie ou video-game u could always start talk to him about that.
then it won't seem like you're desperate :) u just want to talk about the awesome thing he brought up to begin with.
don't think it'll work unless u hang out in the same circles though... 'cuz if u don't it might seem wierd to just jump into a conversation, just sayin'.

Say hi and talk to him like toi would normally talk to anyone else.

Just ask him about anything

His favori movie
His favori reality TV show
His favori snack
His favori electronic device
favori game
favori subject
If he's in any of ur classes

.....so on