Well lets list these in order
1. If he goes to your school you can look in the directery
2. If you know any of his friends ask them for it, or ask your friend who knows everything
3. look in the...
Step one is to prepare the ground. If you ask for his number before he's ready to give it, what are you going to say on the phone? "Hello, you don't know me, but I think you're cute...?" Work at the...