Well, a veteran official around here has always told me before a game: "Don't fu** up." I try to take that on out on the field and court.
No, listen to every piece of advice you can get. There are a lot of good umpires (or other officials) who have been there and want to help. Find someone you can look up to and watch them work. Hopefully, someone in your group will take a liking to you and take you under their wing and help out.
Best of luck.