How do I talk to my crush's friends and not sound like a complete idiot?

My crush has asked me to her birthday meal this wednesday and I've never met any of her friends before. I'm incredibly nervous (and mega excited at the same time) because I'm quite a shy and quiet person and I'm afraid I'm going to either say something extremely stupid or worse, nothing at all! And they're all a year older than me so I already feel slightly intimidated by them.... help please? What shall I talk about? How should I start the conversation?!