Unfortunately, LARPing can be a bit tricky to get into. Although some LARP events are held at relatively public functions, such as science fiction or gaming conventions, many of them take place on private property and can be hard to stumble across. But despite logistical concerns, LARPers are an accepting bunch, and always in need of new players. Even more so than tabletop role playing, LARPing needs a constant influx of new people to survive. Even the smallest LARP events tend to require many more people than a standard tabletop game.
New faces are always welcome.
There is a fairly active email mailing list devoted to discussion of LARP topics. Larpa-gen is open to all subscribers. Many science fiction and gaming conventions will have a LARP or two lurking around in the shadows. Check out conventions in your area and scan through their program guide. An important thing to remember about LARPing is that it's a fairly broad activity.