Mike,
I chartered with Footloose in BVI last March through Ed Hamilton. Footloose is part of Moorings (just older boats and less expensive). They require a sailing resume describing your experience with boats of similar size to what you will be chartering. If they suspect that your experience is insufficient, they will require you to take on a check-out captain for a couple of hours to show your skills (not as traumatic as it sounds). If everything is OK he asks you to drop him off and away you go (minus a fee for his services, of course). If he isn't satisfied, I guess, he stays on board for the week. Our check-out went well and the captain was a really interesting guy. We had an absolutely fantastic week. Footloose does a great job and I would recommend them to anyone. To answer your question, you leave the boat like you found it. Where do you plan to charter? Any other questions, let me know.
Gary'Expresso''75 C&C 35 Mk II East Greenwich, RI, USA

I've chartered numerous times from Sunsail, Tropic Island, and Sun Yachts - all in the BVI. My experience has been similar to what Gary mentioned. You send them a sailing resume. If you have some experience and know how to handle a boat - it shouldn't be a problem. If they are not comfortable with you level of "boat handling ability", they will throw a captain on until the capt feels you can handle the boat yourself. My best experiences have been with Sun Yachts in Tortola. I was not a boat owner the first few times I chartered, but I had a pretty experienced crew. I think that helps. Any other questions - let me know