I totally agree with Connor. I think that you should definately make a list of things to say, it'll make you less nervous, and you'll be more confident around people
I used to be like that with guys, especially with the ones I liked. I used to just stand there when they'd talk to me... haha... with this one guy, it took me 2 months just to say hi even though we'd see each other all of the time! haha...
Anyway, what got me over that is: 1. do what Connor said, a list def helps!
2. I would not think of the guy as "the really nice, hott, athletic, smart, funny guy that I really like that I would never be able to go out with because 'I'm not good enough'." Doing that just makes you so nervous and the other person will think you live in a box or something and we don't want that.
Basically, if you do stuff like that, you'll be much more confident and you won't need the list anymore. Not to mention, a lot of girls will notice your self confidence!