How do I get this guy to see I'm interested in him?

So, I met this guy at one of my friend's birthday parties and now I sit at their lunch table. He's cute and makes me laugh and he's got me interested in him. He seems to flirt with me and he smiles a lot when I talk to him, but I'm not sure if he's interested in me or if it's just his personality. He's a freshman and I'm a sophomore, so I don't see him in any classes but lunch. How do I get him to see I'm interested or get him to ask me for my number? I would really like to get to know him better. Please help me. :]