When you're sailing on the water, pack light layers that can withstand hot, hot heat and chilling ocean winds. Nautical colors like navy blue, white and red are classic. My clothing during the day ranged from a swimsuit with a light wrap to white shorts and a red striped t-shirt with bare feet. At night, we warmed up with chunky knit sweaters, warm long pants, and topsider shoes. I loved wearing comfortable clothing that made me feel chic.
Pack extras in case of emergency. For sailing, bring a large first-aid kit, barrels of fresh water, and lots of food. For cruising, have emergency medicine and a copy of your passport.
If you're sailing on a boat, try catching some fresh seafood while you're out there. Put it in a risotto with some mushrooms, and you've got a great, fresh dinner.
When you get to a port town, the locals will be expecting tourists and have “authentic” goods to sell. Get inland a little bit to where the “real” culture of your destination lies.
Bring along a few crewmembers to man the boat for you while you relax. Otherwise, you'll have to be at the wheel 24/7, which doesn't seem like much of a vacation.