Liquids and electricity don’t mix. Keep drinks, potted plants, etc. away from your computer.
The first thing if there is a spill is: Immediately turn the computer off, unplug it (or remove the battery if it is a laptop). Wireless keyboards and mice also have their own batteries which should be removed.
If you leave the battery in, there is still current flowing in the machine and that’s what you DON’T want to happen when there is water to short between circuits.
Turn the keyboard or laptop upside down. Blot up all the water you can reach with a paper towel. If it is a bad spill, disassemble the machine to give access to blotting up the water.
Now leave the machine in a warm place for at least 48 hours until it is thoroughly dry. DO NOT TEST IT before then to ‘see if it works’ – by applying current to the circuits you may be administering the coup de grace.
http://tech.yahoo.com/gd/saving-your-laptop-after-a-spill/153194
After that it depends on what type of liquid it was. Anything with sugar (pop, milk) or acids (pop, tea) or salts will leave a residue on the components which can create a short, or eat away at the connections (like a battery that leaked in a flashlight). Sugars can also gum up keyboards and switches. If you have a bad spill of this type of liquid, the machine will need to be disassembled and carefully washed and dried with distilled water and/or alcohol.
Some people recommend putting the keyboard or machine in a bag with rice, under the assumption that the rice will absorb the moisture. I’m not a fan of this, it’s impossible to stop the rice dust and fragments from getting into the keyboard. I think putting it in a warm place with good airflow (like on top of the fridge or hot water heater, maybe with a fan on it) is preferable, unless you live in an environment with 100% humidity.