Be good at small talk.
Many of the jobs you get at first will only be a day, maybe two. You're going to be making a LOT of small talk with people.
Get some conversational skills. Ask polite, but appropriate questions. Practice listening (it's called small talk, because you should listen more;)
And here's a really good one; try to remember one distinct thing about each person. Even if you don't remember a person's name, if the next time you see them, you can say, "Didn't you tell me about a great place for pizza in Austin?" They'll be both surprised and delighted that you remembered something unique about them.
If you remember their name too...even better.
So, remember that shirt you were so awesome about putting on before you sat down to get your make-up and hair done?
It's got a secondary purpose. It's multifunctional. Yeah, that's how awesome this shirt is.
Your On-Set Shirt should also be a little bit big for you. Big enough that you can throw it on easily over whatever other wardrobe you're wearing.
Why is this important? Because, hopefully, at some point, you're going to break for lunch. When you do, you're going to be able to save yourself some hassle by being able to put your "On Set Shirt" on right over your regular wardrobe. I know, so frikkin' genius.
This will stop you from getting food all over yourself, and, therefore, will keep wardrobe happy, and make you look more professional, because you are. Wardrobe and make-up are both in charge of how you look, so making their jobs easier, and less stressful is going to make you look that much better for the final product.
I know, I know. You don't spill food on yourself when you eat. Yeah, yeah. Neither do I. But you know what, it's a good thing I've had that damn shirt on, more than once. Cause sometimes, there's ice cream for dessert.
You should own a snap-up, or button up shirt that's a little too big for you, that's not offensive, or some crazy color. Something from Target is fine. This shirt will have one purpose and one purpose only.
It is your On Set Shirt. Yeah, I capitalized, it's a proper name.
I'm not saying that you have to where this shirt TO the set, but it's going to help you out once you get ON set. Here's why.
Say you're sitting in the make-up chair, and the hair person just finished about 20 minutes (if your a guy) or an hours (if your a gal) of work. You then go over to wardrobe to get your stuff. What happens then? Before you can put your wardrobe on, you've got to take your t-shirt off...over your head.
You're about to ruin someone's work, and they're going to have to come touch you up. Before the shoot even starts.
Once you get to set, and have made your impression with you're awesome sense of style. Change into your on-set shirt before sitting down in the make up chair. When you're done, and it's time to change, you don't have to worry about messing up someone else's hard work as the first thing you do on set.
There's another reason you should have an onset shirt, we're not done yet.
So, you booked a gig. Sweetness. The fun isn't over. You've actually got to do the job and at the very least not embarrass yourself.
The first thing you should do when you get on set is to ask who the 2nd Assistant Director is. This is the person who is, essentially, "in charge" of you.
Reporting to this person once you get to set is key, since you'll wan them to know where you are at all times. Nothing too extreme needs to be said once you find this person. Something simple like, "Hi, I'm AP. I'm one of your actors today."
They'll show you to your trailer, room, or to wardrobe, depending on the location & budget of the shoot.
If you are going to be anywhere other than your trailer or on set, you should let the 2nd director, or some other friend you've made with a walkie talkie know. Make-up o wardrobe will tend to be around, and if you need to run to the rest room, letting them know is alright as well.
Basically, let SOMEONE know where you are at all times. You may think that you have an hour before they shoot, but nothing's worse than finally having the sun in the right spot to get the perfect shot and they can't find the actor.
Don't be that guy. Please.