For electronics without LCD screens it is easy:
1. Do not power on or fire the device. If the battery is removable, do so immediately.
2. Fully submerge in rubbing alcohol (preferably the 90+% stuff) just long enough that it can fully penetrate the device in order to reach any water/moisture that is present. This step may damage paint or other finishes and will ruin LCD screens so use caution.
3. Dry using a paper towel, microfiber, hand to towel, or whatever else you have.
4. Place device in an OPEN bowl of rice with the device fully covered in rice or similar product for a day.
Damage to electronics from water comes from 2 possibilities. 1. a short due to the water which damages a component. This occurs when electricity flows through the device while it is wet. 2. Corrosion. This is a result of water sitting for too long. Removing the battery immediately and not attempting to power on or using the device until after the drying process is complete. The second issue is solved by the use of rubbing alcohol. Rubbing alcohol is safe to use on electronic circuits and displaces and dilutes any water that is present. Since rubbing alcohol evaporates much more rapidly than water it also reduces the water exposure which reduces the chances of corrosion. The rice is a safety net to ensure that the alcohol is fully removed and that any remaining water is removed with it. You leave it open to allow evaporation to occur so that water and remaining alcohol is evaporated or absorbed.
For a device with an LCD screen, just remove the batty as quickly as possible and put it in rice for a minimum of 3-4 days and keep your fingers crossed.