Talk to him. Considering he is new to the school, he will probably appreciate someone else taking the initiative to come and make conversation with him. He is probably secretly too shy to just go up to randoms and say hey. The earlier you get in and start talking to him, the easier it will be. If you leave it too long, he will get other friends, and maybe it will be harder for you to talk to him then.
Just tell him he is welcome to come sit with you whenever he wants. Ask him where he moved from, and why, and a couple things about his hometown etc. I'm sure he would love the fact that you took the time and guts to make him feel a bit more comfortable at his new school. And you always remember your first few friends at a new school, the ones who were there for you from the get-go.