I heartily second the advice to profile your desires. You really need to write down the things that you've heard/read about that turn you on. And experienced dominant will be able to let you know what might be too intense for a beginner. (Yes, I recommend experienced dommes for beginners just because they have a better idea of how to structure a session that you can enjoy while learning a few things.)
Don't try to tell the dominant how to run the session, but make sure you tell her your limits (I once had a guy tell me celery was a limit. I never did figure that one out.), any medical problems you have, medication you're on, and whether or not marks are a problem. (That can help her decide on things you want to try. If marks are a problem, there are some SM activities that are a no-no.)
None of us are mind readers, so if you can bring her a list saying that you want to try W, Xand Z and that Y is a limit, you're much more likely to have a good time than if you show up and say, "I wanna explore." What if she makes you be a puppy for the session when what you wanted to explore was SM? What if you wanted to try humiliation and she did a sensual spanking?
The more she knows in advance, the better your session will be.
Also, if you want strap on play, you need to specify that in initial negotiations. Not all dommes do that. Not all dommes do everything, so the more information you can provide, the better your session is likely to be.