Sign up to the Jack Rabbit Speaks newsletter and your local regional group's mailing list, they'll have information in the spring about volunteering/participating with different departments, I believe.
As a rule, though, in your first year you shouldn't plan or schedule volunteer shifts in advance. For starters, your presence on the playa is a gift to the community - just worry about getting out there in one piece and enjoying the experience. Second, as you'll probably discover over the course of the next ten months, getting out there takes a lot more than most people imagine. Regardless of the experience you may have with camping or anything else related... Burning Man is something else. If you sign up for a bunch of stuff, you may find yourself in a situation where things get overwhelming as the event approaches (or you get out there). Then there's also a certain 'holy shit' factor, where new folks who are prepared and ready to go get out there and just get completely lost (in a very good way), and for one reason or another have incredible difficulty honoring any of those commitments (which then sucks for the group that was in need of help).
Don't worry though, there will be plenty of opportunities for volunteering and pitching in on the playa. Head to Playa Info (next to Center Camp) on any given day, I believe there's a temporary job service that helps put volunteers in touch with artists and projects that can use a hand immediately. There's also the Lamplighters (also near Center Camp), hit them up on any afternoon and you can help them light the streets of Black Rock City. And there's BRCPO - the post office, which can also put volunteers to work every day, delivering packages and messages to points all around Black Rock City. I'm sure there are other 'on the day' volunteer options too.
Good luck, and hope to see you out there