When your iPhone's wet, speed is essential. Turn off your phone to avoid a damaging electrical short. Don't shake the phone vigorously, encouraging water to travel further across the circuit board. Don't leave it on the radiator, in the dryer or the oven or use a blow dryer on it. Don't freeze it; cold iPhones attract condensation. Warm is good, hot and cold are not.
Dry Your IPhone
Remove the protective case and SIM card. Towel-dry the phone and card. Seal your iPhone in a quart-sized baggie, sandwiched between two DampRid sachets or buried in silica gel packets. Alternatively, use instant rice or low-dust kitty litter as you head to the store for DampRid. Leave your bagged iPhone off for at least 72 hours. Then, if your iPhone powers on, heave a sigh of relief! However, keep in mind that if water -- or worse, chlorine or salt -- stay trapped deep inside, components may corrode and lead to eventual iPhone failure even months later.
Check Your Insurance
If your iPhone doesn't come on after 72 hours, check to see if you purchased accidental damage insurance with your phone. At the time of publication, the insurance sold by most carriers has a $200 deductible for an iPhone 6, whereas AppleCare+ or SquareTrade insurance both have deductibles of around $80.
Repair Your Phone
Your best chance of reviving your iPhone is to bring it in for repair right away. It's not the cheapest solution, but if your iPhone has been drying for a few days to no avail, a knowledgeable technician could possibly resuscitate it by opening it, cleaning it and changing the battery.