Water, Water, Everywhere!
Water is one of the worst enemies of the camera, capable of everything from frying out the circuits to depositing difficult-to-remove scum on the optics to destroying the LCD screen. It doesn't matter whether you're on the beach or in the rain, it's a dangerous environment for your camera.
The best thing you can do for your camera? Don't take it to the places where water's a real risk factor. If it's pouring outside and you're going to be out in the rain all day, it's really probably not the best idea to bring it with, even if you have all the rain gear in the world. Salt water in particular can cause corrosion, which is difficult to deal with.
That being said, a lot of times you just really need that camera around for those once-in-a-lifetime shots. There's a lot you can do to prevent water damage.
Consider purchasing a waterproof or water resistant camera case, one that is rugged enough to stand up to both natural and human elements, for between shots. Failing that, even just covering your bags in plastic wrapping will save it a lot of moisture damage.
Other accessories can also help keep your camera safe. Rain hoods are helpful if you absolutely have to get that shot in the pouring rain, though even with the most careful handling a few drops will always get in.
Dry your hands before handling the camera, even so much as taking it out of the case. Also, make sure that for those small droplets that you have some soft, dry lens cloths around to wipe it off.
For more information on how to take care of water damage, check out this article.