Of all the things that an actor could or should do, there are two things that are the absolute minimum requirements for being an actor:
Memorize your lines. Know where you’re supposed to be on stage, and when.
Notice I haven’t mentioned anything about the quality of your performance, your choices for the role, whether or not you stay in the moment, or any of the other things that we hope that you manage to do on stage. I’m simply talking about basic, foundational needs. If you do these two things, you can get through a play start to finish without major mishaps.
If you don’t do these things, then it doesn’t matter how well you know your character, whether or not you’ve made the most interesting character choices, or how effectively you deliver your lines. If you can’t remember them to say them, everything else is irrelevant. If you can’t remember where you’re supposed to be and now you have to leap across the stage in order to open the door for someone who the audience doesn’t know is going to be there, it will look contrived. If you are supposed to cross left and you don’t, and you create a traffic jam instead, that’s a problem.
Please remember, the audience isn’t stupid. They admire the fact that you can memorize all those lines, because they can’t, but because it is inconceivable to them, they expect it of you. Paraphrase, improvise, and they probably won’t notice. Drop a line and recover fairly quickly, and they’ll forgive and forget. Drop a few, even if you recover quickly, and they’ll talk about it on the way home in the car. Forget more than that, or forget them in a way that causes some obvious major problems, and they will be livid. There is an unwritten pact with the audience, and that pact is that they will give you a few hours of their lives in exchange for you memorizing your lines and moving around the stage the way you’re supposed to. Break that pact, and they will not only see you as unprofessional (whether you are an amateur or not, they expect you to behave professionally), but they will take it personally.
The bare minimum is that you should be completely, solidly off-book no later than two weeks before you open. The recommended minimum is that you should reach that point no later than three weeks before you open. If you can manage it earlier, it’s probably going to translate into a much superior performance than you would otherwise have had, and it’s also going to mean that you will be better able to bail out your fellow actors if they should go up on their lines.
Many years ago, I was in a six character play, and we were all on stage at the same time. Five of us went up, and we had no idea where we were or what came next. Fortunately for us, the sixth actor knew exactly where we were, because he really knew the play backwards and forwards. I suspect he’d actually memorized most of it, but even if he hadn’t, he knew the flow of the play, what each beat was about and the material content and exposition in each beat. He could have gotten us out of any jam that we got ourselves in, because he knew the play that well.
Because of that experience, I realized that MY responsibility as an actor is not only to memorize my lines for the audience, but to also memorize them so that I didn’t let my fellow actors down. If I forget my lines, I put my scene partners in a difficult situation. Not only am I asking them to bail me out, but I might go up in a section that makes it very hard for them to do so without it looking incredibly obvious to the audience.
And beyond that, I decided that I wanted to be that sixth actor. I wanted some control of my own destiny, so that if someone else went up on their lines, I could not only bail them out, but I could make myself look good on stage. In making them look good, I would also make myself look good. After all, the audience doesn’t always know just which actor has forgotten their lines. I wanted to be sure that they didn’t think it was me.
And perhaps most importantly, I recognized that we are all going to forget a line every once in a while. We’re human, and it’s simply going to happen. Better to be prepared, I thought, for that eventuality. So I learned to make sure that I really understood the play, and why this thing had to happen before that thing, and why it was natural for this to follow that. Why these lines belonged in this particular section.
As a result, years later, I was in a production of Woman in Mind, and the actress playing my sister-in-law walked onstage a page and a half earlier than she was supposed to. The actor onstage with me at the time and I had to go with her scene, and when she exited, I jumped back to the line we had left off on when she had wandered into the scene. We played the page and a half, and then I jumped ahead to what happened just after she exited, and we were back on track again.
I could see the panic in the third actor’s eyes when she came on stage early, and the fear because he knew that we couldn’t lose the page and a half, from a dramatic perspective. Fortunately, I knew the play well enough that I knew how to navigate our way, and he just followed my lead. And in doing so, paid an outstanding debt to that sixth actor so many years ago.
If you have trouble memorizing your lines, then you’d better start working on them from the day you get your script. Check your progress against the calendar to be sure you know how you’re doing against the deadline you or the director has set. Actively work on your lines, and don’t expect them to seep into your brain through osmosis or rehearsals.
Similarly, memorize your blocking. This is something you need to work on at home, not just during rehearsal. Do your homework and come to rehearsal prepared. Respect your fellow actors enough to do that for them.
I once directed an actor who told me he hates blocking. I’m sorry, but that’s not an excuse for not learning it early. Memorizing your lines and your blocking are your primary jobs as an actor; don’t whine or offer excuses, just do it. Or else don’t act. These are not negotiable; they are the essence of what you are supposed to do.