make sure you know and understand the clubs rules for safety... typically:
a. alll guns have to be unloaded ..unless you are on the shooting station in the trap, skeet or sporting clays field. That means no shells in the magazine of a pump or semi-auto either.../ no shells in a side by side or over under, even if its broken open as you move around the club.
Games like Trap singles...mean you can never have more than 1 shell in your gun at any time.../ and never when you move between stations.
Some games ( on some stations of Skeet ...and in sporting clays ) you can often load 2 shells...but never more than 2...it doesn't matter how many shells your gun will hold in a magazine.....
b. from the time you uncase a gun ...open the action.../ break it open if its an Over Under....open and lock the bolt open if its a semi-auto ...and open the pump if its a pump gun...and keep it open .../ and no shells in it ...as you leave your vehicle and move around the club.
c. check your shells....most clubs limit you to shells with shot no bigger than 7 1/2's ( no 6's, 4's, etc...) ....only 7 1/2's, 8's or 9's....some clubs are restrictive on velocity as well ...but you're usually ok, if your shells are no faster than 1200 fps...
d. make sure you know how to operate your gun .. especially if it has a safety that automatically engages as you close the gun ....so you don't waste targets ( they may charge you for extras). Make sure your gun is well lubed...so it operates with no problems. Guys that bring out grandpa's 1950's semi-auto that hasn't been cleaned or lubed in 19 yrs ...hold up the squads in the field....
e. many clubs limit shotguns ...to guns that have barrels no less than 24" long...so call ahead if that's an issue.
f. be friendly ...and ask for help .../ see if they have a member or someone that will help you out ...give you some tips / etc...
Be Safe ....and Have Fun !! ...and welcome to our side of the hobby ! Its addicting...
Most of this is Courtesy and Common Sense...