A good way to be more comfortable around strangers is to have someone with you that you already know. If your friend is more outgoing, he can help you easily integrate into existing groups and conversations.
If possible, find someone you already know who's in the group and hang with them. Odds are good that they'll talk to others and include you in the conversation.
Find someone like you.
One of the biggest challenges shy people face in new environments is feeling like they don't belong. It can seem daunting to fit in when your mind is telling you all the reasons you should be embarrassed. But if you look for someone like you, you can rest easy knowing that you're both nervous so you can help each other to adapt to the social pressure you both feel.