Grrrr, how do I overcome my shyness?

So, I went into the library since we had just finished an exam for P.E. and saw this guy I was interested in in there. I first sat behind him, but then sat right next to him at the computer lab and was so nervous. I was going to talk to him, but then he left like five minutes later (yes, I couldn't say anything in that time). How do I overcome my shyness? He's one of the LEAST popular guys in school so it should be easy, right? AGHHHHH. I have him in 6th too and I WILL talk to him! Argh! :( Help? What do I say?!