I like a guy in some of my classes. How do I get him to ask me out if he's a shy guy?

Ok, so I really like this guy who is in some of my classes. He already knows, i emailed him on Valentine's Day this year. We are both kind of nerds and we have a lot in common. We email back and forth but I feel like I am the one that initiates the convos, but he does a little bit. He isn't shy around his friends but he is around everyone else, especially me. I catch him staring at me at least once in every class, sometimes he'll smile and sometimes look away quickly. His best friend likes me and I think he likes me but doesn't want to admit it. I have a more outgoing personality somewhat, so I wonder sometimes if I am scaring him away.