Drip and splash photos have always fascinated me for their sculptural quality. For a really supercharged effect, I go for bright, highly saturated, and contrasting colors.
I'm always on the lookout for potential backgrounds with rich color and reflective surfaces; in addition to high-gloss photos made especially for the purpose, I've used gift wrap and even ashtrays! I look for boldly patterned backdrops, too; often the pattern will be reproduced in the water drop itself. The receptacle to catch the drips or splashes should be colorful, as well-preferably a tone that contrasts with the background.
Water drops reflect an area of about 120 degrees behind them, so I draw a mental arc to that size, and look for backgrounds wide enough to span it. Because the background sits only 2 to 4 inches behind the subject position, the backgrounds don't need to be too large.
I start by mounting my Canon EOS 20D and Sigma 150mm f/2.8 macro lens on a tripod in front of the set. Looking through the viewfinder, I shift the background until its color reflects most strongly off the surface of the water. I use only manual focus. As a target for focusing, I put a UPC bar code (from a milk carton) in the drop's path. An aperture of f/4 or f/4.5 gives enough depth of field to keep the drop sharp while blurring the background.
An eyedropper sends the drip on its way, and the instantaneous pops of multiple flash guns freeze the water drop mid-flight. I surround the set with two or three inexpensive, slave-activated units to light the background and subject equally. I dim the room lights, open the shutter for three to five seconds, squeeze a drop into the receiving dish, and pop one of the flashes manually, which causes all to fire in tandem. I repeat it until I get the result I want.