2nd, when you do make a mistake, dont' EVER stop playing. Ever Ever Ever. You have to move on and stay with the rest of the band.
With time you'll learn what they are doing and you'll make fewer and fewer mistakes. You'll also learn to anticipate certain things like vocal queues and riff queues. These will help you remember what to do next.
As stated earlier, you need to get the music they play and learn it. Practice each day. Perhaps you can get a recording of the band and use it as a backing track.
Playing with others, IMO is the really rewarding part of being able to play.
Good luck.