This is a really good question! I'll throw in my very limited opinion - I'm sure there are others more experienced than I who will have better advice.

Physically - it sounds like you're in great shape! Flexibility is a big plus, so you may want to begin daily stretching exercises to maximize that.

Mentally - this is the big one. Confidence is a big plus. Confidence that you're worthwhile, confidence that you are able to be pleasing, confidence that you have something to offer. Most Doms DO NOT want a whiny doormat.

Also, know that this is what you want. Really know. Understand that it's not all fantasy. Ropes fray, muscles get pulled, knots don't tie right, and generally, silly stuff happens. Can you go with the flow and laugh when that happens? Being able to understand that yes, this is serious, but yet not take yourself too seriously, is a wonderful quality for a submissive to have.

Finally, do you love you? If you don't, figure out why and either change it or accept it. If you don't love yourself, you'll sabotage your own efforts to submit. Not a good thing. And don't expect a Dom to "fix" you. They may be willing to help you change things about yourself, but they aren't there to prop you up all the time. In the words of the Wizard: "I don't want to be picking up the broken pieces of her psyche every time we play." Or something to that effect.