Rent a car unless you can find a place to stay in Cruz Bay. I would still recommend one even if you are staying there tho. There are so many places to visit. Having a car is a necessity otherwise. I think it's around $70/day.

Out of St Thomas. Look up the ferry scheduled to Cruz Bay. You can leave out of Charlotte Amale(sp?) or Red Hook. You have to take a cab to either one of these but Charlotte Amale is the easiest and cheapest, but it runs less frequently.

Cool bars: there are a bunch in Cruz Bay. Check out Woody's. The places along the water in Cruz Bay are all pretty cool.

Nice restaurants. Zozo's. Very expensive but one of the coolest atmospheres and best food I've ever had.

Take a day trip to Jost Van Dyke. Trust me it will probably be the highlight of your trip.