Remove the unit cover and disconnect the battery. After that remove SIM card and memory card. Put them out to dry at room temperature, in any case, do not try to speed up the process with a hair dryer or radiator. If the phone is dropped into water during charging (for example, dropped it in the indoor aquarium), first disconnect the charger from the mains and then remove the device from the water. If dropped in the water the device was connected to the computer, before removing it from the water disconnect the cable from the computer.
Buy a special screwdriver for disassembly of cell phones. Normal screwdrivers do not fit, they will only ruin the splines, and dismantling the device will become very difficult. Then all depends on the form factor of a mobile phone. If it's a monoblock, disassembly does not require special explanation. If before you a slider or clamshell, be sure to find in the Internet detailed and illustrated instructions for the dismantling of this model.
If the phone has been exposed to salt water, wash all parts except the display and battery with distilled water. For the apparatus, which sank in fresh water, you can skip this step. Then place all parts except display and battery, pure alcohol (vodka is not necessary) and will hold there for a few hours. Out of alcohol, let them dry, which will require the day. There is also not allowed to use Hairdryers and other heating devices.
Assemble the phone in reverse order, install a SIM card, memory card and battery. If the water was salt, the latter preferably to be replaced. Turn on the machine and verify that it works. Over the next month use of the phone you'll know exactly whether he was to malfunction or the quality of his work has not changed.