I don't think you can be more awkward than Kristen Stewart...
Just start with "Hey, how's it going?" Then pick something about him, like his glasses (if he wears them), a watch, shoes, shirt, etc. Anything you can, and compliment him. Because who doesn't like compliments? See how he responds, keep the conversation going the best you can, and as soon as you detect an awkward silence coming, say "well, I'll catch ya later!" Or something like that. The confidence of knowing what you're doing will most likely impress him. I wish you the best :)
Pretend you don't have a crush on him and just try to talk about something like he is a friend or someone you are comfortable. Fake it until you are actually comfortable.
free your mind.