How to talk to people in groups?

Hey there folks. I'm heading to a church camp in a week's time and want to make some friends there. Now I will say I have been guilty of this exact same thing in the past, but people tend to stay in their wee church groups and not stray far away and I don't really know how to make conversation with a group. It always ends up like I'm speaking at them not with them and sort of barging in on their conversation. What do you do? Cheers guys