A Girl at my College that I Like?

Just go ahead and message her. If you are afraid of rejection you don't have to ask her out right away. Start a conversation with her. Once you two get closer then ask her out. You won't be as scared once you get to know her a little. As for messaging her the first time say something like "You go to (Insert College Name Here) right? I think we had a math class together. I never got a chance to talk to you, so I thought I would message you." Hope this helps :)