Here are a few things by which you must absolutely abide:
Be on time. Scratch that – show up 15 minutes early. No excuses about traffic or parking. The shittiest feeling in the world is running late, stuck in traffic, and then your cell rings, and you just know they’re looking for you. Trust me – tying to race to a set in LA morning rush-hour traffic is the worst Grand Theft Auto game ever.
Papers, Jew. Make sure you have your license and/or passport with you. This is a job, and it requires a 1099 just like a civilian job. Having your IDs with you and filling out any paperwork immediately endears you to the assistant directors, who are some of the biggest gatekeepers on set. But disappoint them, and just go ahead and give yourself a purple nurple.
Shut your yapper. Chances are, cameras are rolling and you don’t want to be shushed while someone else is being filmed. And don’t wander off to craft services without letting someone know. You don’t want people looking for you. Instead, you’re going to be the agreeable, available Johnny-on-the-spot. The actor they absolutely must work with again. The DeNiro to their Scorcese. Until Scorcese leaves your ass for DiCaprio.
Respect the garments and whatnot. The wardrobe people bust their asses to make you look good, so hang your clothes back up when you’re wrapped, and walk them back to their department. I’ve watched actors just drop their clothing on set, or leave them strewn about their trailer. And give your props (watches, guns, etc.) back to the prop master. He’s responsible for that stuff, and his main responsibility after an actor doesn't return props is figuring out what to do with his corpse.
Be prepared, fool. Have your lines memorized. There’s always the chance your scenes will be shot out of order, and your brain has to be ready for that. It’ll be a big cast and crew standing around you – don’t hold them up doing multiple takes because you keep going up on lines. Instant flop-sweat.
Lucky for us, there are a couple of great ways to practice set etiquette from the moment you arrive in LA: booking roles in student films, which in every way are microcosms of big TV and movie shoots, and doing extra work. But only do background a couple of times to get a feel for sets and see how the talent go about their business. You’re no extra; you’re an actor, with a day-job that allows you time to audition for acting work. And then book that work. And then behave. Like a boss.