Telling a guy that you like him is no big deal. Really. What's the worst that could happen? We did a little survey. Here are some responses:
"He could say no." - Vaishali, 23
"He could laugh! Imagine the shame!"- Sheila, 23
"He could introduce me to his girlfriend." - Mahima, 25
"He could hear me!" - Sapna, 22

All right, so things can go wrong. Maybe he won't respond quite like you hoped he would. Maybe he will. That's beside the point. The important thing here is to come out of the situation like a cool dudette - irrespective of the outcome.

The Build-Up
Do smile at him a lot. (Don't overdo it. It'll scare him if you grin like a moron every time he looks at you).
Do find ways of being in the same vicinity as he is, so you can start a conversation (at lunch, while you're hanging out with friends, etc).
Do ask him out. If you are afraid of how it may look, make plans in a group and insist that he come.
Do give him special attention when you guys are in a group.
Do encourage closeness. Share thoughts; debate over different ideas (it's loads of fun).
Do fun things together. Go for drives, late night desserts. Lots of friends do these things together. And if he gets the hint along the way, all the better for you!