There are a number of techniques for retrieving a person who has fallen overboard but the Williamson Turn is one of the more popular ones for power boaters and is taught by both the U.S. Power Squadrons and the U.S. Coast Guard Auxiliary. Below are the procedures for using this technique to get an overboard person safely aboard:
If you can see the person in the water clearly, a simple 180 degree turn is the quickest.
If you lose sight of the person, due to poor visibility, or heavy weather and sea state, the 'Williamson turn' is a good way to get on to a reciprocal course which will take you back down your track:
Put your helm hard over to the starboard and add 60 degrees to your course. When the compass is reading course + 180 degrees, steer a reciprocal course and the casualty should be ahead of you.
In heavy weather the reciprocal course may bring the sea astern, in which case a short approach head to sea may be more appropriate once the turn has been completed.
Do not waste time while the boat is turning to approach the person in the water - prepare for the recovery as it is too late when they are alongside.
Which side will you approach? Have a heaving line ready and wear a lifejacket and lifeline; if you don't, you may get pulled on top of the person in the water.
The initial approach to the person in the water will vary depending on weather/sea conditions and the type of boat. Let the weather help rather than hinder - stop unwind and drift down.
If you are concerned about drifting onto the person in the water, bring your stern into the wind. If you're not confident with your boat handling skills, or if it looks likely that the boat could come down on top of the person in the water, throw them the heaving line and pull them alongside to a safe place for recovery.
Ensure the propeller is not turning when you are alongside the person in the water.