Look and present professionally. Observe the crew your riding with closely and don't take everything they say or do as the absolute truth. Ponder your experiences and research them for yourself.
Since its your first shift, show that you respect the more experienced staff by not getting into racy debates or anything too soon. At least until your established as a staff member, i agree with the think before you speak comment as well. Most important.. HAVE FUN! thats what its all about, it makes for a very long day if your not having fun at work. Good Luck!!