I teach a lot of students, beginners and professionals alike, about acting. The number one thing I feel every new actor must drill into their head is professionalism. Professionalism is the easiest way to separate yourself from the pack. Professionalism is about consistency. If people know they can count on you, it could be the difference between you booking another job with the same people or not booking it. Commitment is everything to an actor; to your craft, to the role, to the production, etc.
One of your biggest assets as an actor is professionalism. You show professionalism through your actions and attitudes. Always be courteous and respectful to anyone you meet. You never know when you might work with them again.