- Keep your shutter speed as fast as you can if you don't plan on using a flash. Even if that means cranking up the ISO. 1/500th even seemed a little slow when I was experimenting with it. Getting up over 1/1000th seems ideal.
- This is one of the rare occasions where using an on-camera flash works totally fine. It will help you freeze the action and because water will be obscuring the face a lot of the time, the shortfalls of the harsh light will actually work in your favor for once.
- Picking a plain background (or using flash and keeping your ambient exposure very dark) will help the water stand out from the background. Leaves and other busy patters make the droplets harder for the eye to pick out.
- Using a light source from behind your subject helps accentuate the water. It doesn't have to be a flash, either. You can use a lamp, or even the sun if you want to. The trick here is that you'll need to keep your shutter speed fast even though you're using a flash, otherwise you'll get blur.
- Give yourself enough depth for field so you can keep most of the water in focus. The sharp droplets really do draw the eye. When they get blurry, the effect isn't as pronounced. Of course, you may like that better, so it's really up to you.
- Remember that water is bad for camera gear so long lenses are your friend. Just be sure to back up enough to leave room in the frame to catch all the splashes.