I've been trying to get my coworkers numbers for what seems like ages now and I can't seem to find the most opportune time. I can't exactly do it at work because i'll get in trouble (and made fun of) by my coworkers. But I see him sometimes at school, very rare, and we have conversations, but I can never muster up the courage to ask him for his number. What is a good way for me to get his number? I'm almost to the point of asking over Facebook, but is that bad?