Not haveing played in public but haveing heard about it from others here is my two bits.

In most of the places that I have heard about there will usually be some Dungeon Monitors (DM's) to make sure that things are being done safely. Though this may not alwayse be the case at all of the parties that you can go to.

There is my two bits, I agree with what others have said, learn about the person first and see if they are for you, if they do not feel right then they are not right.