Highlight the background, not a splash:
When working with clear liquid (water is the most common example of such), use lights to highlight the background, not a liquid directly.
Do not mix the lights:
Every light should have short enough duration. You can’t use 2 Speediltes and one Alienbees (or any other “regular” strobe) to get shot done: the longest flash duration will inevitably create motion blur. If you mix, make sure the slowest flash has short enough duration to freeze the motion.
Do not try to stop action with fast shutter:
It is a short flash duration is what stops action. Not a fast shutter speed. Do not ask “what shutter speed it was?” as it does not matter, 1/60 or 1/600 (talking about strobe lit studio shots here).
Do not use strobe at it’s full power:
Most of the digital strobes (hot-shoe battery powered Speedlites and PCB Einsteins) will have shorter flash duration at lower power level. You won’t be able to freeze splash at full power with ANY strobe.
1/2000 or shorter is what needed to freeze most of splashes. Smaller droplets have much higher velocity, and if you going to have more of them you will need 1/4000-1/6000 sec of duration for a flash impulse.
Do not use hi-sped (FP) mode when working with Canon or Nikon hot-shoe strobes:
You do not want to use FP shooting mode. In this mode flash is able to sync with any shutter speed, up to 1/8000, but it happens with a huge loss of effective flash power. Meaning you won’t be able to close the aperture enough to get good DOF (believe me, you will need a really good DOF to get good looking splash).
Instead, use the flash in manual mode, set to 1/4 or lower power level, and it will give you 1/4000 sec or even shorter flash duration. Camera shutter should be set to x-sync speed (1/160-1/250 sec, deepens from the camera).
Remember to protect your lights from the spills.
Clear plastic bags would work for little battery powered units, something more serious for large monolights will be required to protect from spills: you can’t cover them with plastic completely, as they will melt it and eventually burn themselves.
Learn how to throw liquid with less turbulence.
The ability to produce a nice looking stream of liquid is essential skill for liquid photograph. This is one of the topics I have covered in masterclass.