An advice would be to look for someone who is not from your class. In the case you only take one or two lectures together, it may be ok, otherwise you will spent all you days thinking about him, and may end up miserable and dishonored by your entire class, if it does not turn out right.
Think carefully before making your decision. If you want to ask him out, just give him your cell number, and tell him that you two should study together, so the phone number may help.
All you need to do is to flirt and make sure you give a good eye contact. You may brief physical contact and ask the guy out on a date. It is important for you to give the guy a good idea of what to expect on the date. You may also decide together what you will do on the date. Visit http://www.ehow.com/how_2004253_ask-guy-date.html for more tips.