How Do I Go Up And Talk To A Shy Guy That I Don't Know?

First off, it is really important that you will have enough confidence to actually go up and talk to him.
If you don't, then when you do go and talk to him, you may have to pretend that he is just like any guy you know ( your brother, a friend etc) and act like you would if you were around them.

Secondly, to seem less like a weirdo you're going to have to look for an excuse to talk to him. It could be anything from something he's wearing, doing, or even if you get a mutual friend to casually introduce you. Or alternatively if you are extremely confident, you may just want to walk up an say 'hi'. Either way he's probably going to admire your confidence.

Just remember, in the best case scenario you will end up with a date or a friend, in the worst case scenario you dont, never see him again and are at the same place you are now.