Talking to new boys

I'm going to my boyfriends birthday party tomorrow, I'm a pretty shy person and it wasn't planned that I would be the only girl going but it's turned out that way.... They'll be him and 4/5 guys and me. I've only spoken briefly to one of these guys and I don't know how to speak to any of them tomorrow night. I don't want to just stand there hanging around my boyfriend all night but I don't know how to engage in conversation with the others as I'm not sure what common interests I have with them ... Advice ??