1. Remove the battery from the device (water and electricity are a bad combination)
2. Get a Ziplock bag or an air-tight container and fill it with dry rice (be sure its dry, LOL)
3. Place the phone in the bag or container and seal it up for a "while" (I've heard timeframes from 8 hours to multiple days--the longer the better in order to wick-away the moisture). You could also replace the dry rice to ensure that you are wicking away more moisture.
4. After you have dried-out the phone as best you can, re-insert the battery and try to start it up.