If you ever drop your phone in water, or get it wet:
DO NOT PUSH ANY BUTTONS, THIS INCLUDES TO POWER IT OFF!!!
Immediately remove the battery.
Place the phone and the battery in a ziploc bag with a couple desicant packs (small bag of beads that says do not eat and comes with your shoes) Sometimes called Silica Gel on the pack. This will help to draw the moisture out. DO NOT TOUCH IT FOR 24 hours or more.
Unlike most items, pushing the power off button actually powers certain circuits to shut down the software. Pulling the battery shuts it down instantly. Electric circuits don't mind water too much unless they are energized. That's when the corrosion starts, which is the problem with small electronics and water damage.
If you really want to give it a good chance, especially if the offending liquid is muddy, or soda/coffee. Open the case and clean it with a toothbrush and distilled water. Then put the pieces in the baggy with the desicant packs.
The battery might be ruined regardless. The battery on most cellphones also have some circuitry inside that is used to regulate current as well as tell the phone (some manufacturers) that the battery is the correct one. That is why some phones (especially older Nokias) don't like the aftermarket chinese battery that you can buy at the mall.
Also, if you are in a place with very little signal, your battery will die much faster than if you have a good strong signal. So if there is no signal, shutting the phone off while it is useless anyway will preserve battery life.