Enter the scene as if you'll be there forever.

Rod Ben Zeev on 13th September 2014, Utrecht (NL)

Never enter the stage with the idea to leave it immediately again. This is about actors entering a scene to deliver a single line, mostly aiming to throw in a quick joke as a waiter, messenger, or what have you.

Don't do that, since it's really just you on yourself having a little plan in your head. Moreover, always be prepared to be kept on stage by your partners, you don't know what's going to happen.