Ok this answer goes for both guys and girls who don't know how to talk to ppl, it's very simple you scan the room and find someone, and then you go up to them and say Hi my name is so and so what's yours? And of course if there are other people in the group introduce yourself to them, and there you go simple as that. One time I saw a girl looking at me at a bar and so I approached her and said hey I saw you staring at me over there and just wanted to say hi, and then we chatted got her number and I think went on a few dates.
Be sneaky, mysterious and whatever you need to get his name by the end of the night. The best route would be the accidental one. Walk by him and accidently hit his shoulder. Remember, this is an accident even if it was on purpose. The two of you will glance and smile at each other while apologizing. He should strike conversation. If he doesn't, ask him if there's any way you can repay him for bumping into him. Be flirty. I am sure you know where to go from here.