Get out there and try! You know that sinking feeling you get whenever you do something awkward? That's a feedback mechanism: don't do things that cause that. Eventually you'll find what works for you and feel comfortable introducing yourself to groups. Even then you'll occasionally have an awkward moment: that's ok! We're all nerds in our own ways, and we've all been there. Just keep moving past it and don't lose your stride (the exact same advice one would give to a dancer or musician for when they mess up).
Hackers and Founders is a great event for this: it's a really great bunch of people. Hunt down Jonathan, the organizer[1] when you get there and explain that you're new to the area and would love to chat with people interested in X, Y, or Z. He'll get you started :). It's much easier to connect with people who share similar interests. Even if you suck at it initially, practice will make you better.
Holding a drink that you can take a sip of is also a great way to avoid awkwardness. As lsb said, cranberry juice (or even water/soda) works just as well as booze.
[1] On the right: http://photos4.meetupstatic.com/photos/event/2/6/5/4/600_168...