Contact the Coastguard Through VHF Radio

Radio procedure for contacting the Coast Guard if either a person or your boat is/are in danger and need to be rescued.

Steps

Turn on your VHF radio.
Tune it to channel 16 156.8Mhz - some radios have a channel 16 button, you can use that.
The Coast Guard monitors Ch16 24/7.
Depending on what you need the Coast Guard for determines how to call the Coast Guard.
If your situation is an absolute life or death situation call out to the Coast Guard using the words "Mayday Mayday Mayday, this is **your boats name** and what your situation is (fire/heart attack/sinking/man overboard etc...)over"
If no response within 10 seconds make another call out in the same manner you did before. Remember, speak slowly and calmly.
When the Coast Guard or similar agency (local police/fire/marina) hails back to you, give them information they ask. They will ask for: Position (Lat and Long, LORAN or Geographic), Nature of Distress, Number of Persons on Board and if they're wearing life jackets, Description of your vessel.
If you don't have time to give all the information, your position is the greatest piece of information you can give. It gives the Coast Guard the fastest way possible to assist you. Don't risk your life trying to give a detailed description of your vessel.
If the situation is not an absolute life or death situation (ran out of gas, engine won't start, fouled prop, requesting weather) simply call out for the Coast Guard. "Coast Guard (geographic area or nearby town) (say this twice) this is the **your vessel name** over"
When they answer back to you tell them what you need on CH16. They will either gather more information on CH16 or shift you to another frequency, like CH22A 157.1Mhz.

Tips

Radio checks clog up CH16 and should be done on a different frequency.
Having your GPS on before calling the Coast Guard saves a lot of time and possibly lives.
Making false distress calls puts many lives at risk and wastes lots of money. For example, in order to use one helicopter to search in America, it costs 3,000 dollars an hour.
If you need help don't be afraid to ask the Coast Guard for it, they can find someone or some way to assist you. They are here to help.

Warnings

Your safety is crucial - don't risk your life in order to just repeat what the CG already knows. You don't have to give every single detail - keep it brief.
In the United States of America, it is a violation of the Federal Communications Act 47 United States Code Section 303 to willfully make a false distress call on CH16 VHF-FM. Current US law states that anyone who willfully communicates a false distress call to the Coast Guard or causes the Coast Guard to attempt to save lives or property when no help is needed is GUILTY of a Class D FELONY. This act is punishable by 5 years imprisonment, a 250,000 dollar fine, a civil penalty of 5,000 dollars and is liable for all cost the Coast Guard incurs as a result of the individual's actions.