Below is an abridged set of guidlines published by the guys at www.americanwhitewater.org.
If you are paddling on moving water but read though this and say uhhhh? then maybe for your own safety and the safety of others you should consider a training workshop.

Guidelines for River Rescue

Recover from an upset with an eskimo roll whenever possible. Evacuate your boat immediately if there is imminent danger of being trapped against rocks, brush, or any other kind of strainer.

If you swim, hold on to your boat. It has much flotation and is easy for rescuers to spot. Get to the upstream end so that you cannot be crushed between a rock and your boat by the force of the current. Persons with good balance may be able to climb on top of a swamped kayak or flipped raft and paddle to shore.

Release your craft if this will improve your chances, especially if the water is cold or dangerous rapids lie ahead. Actively attempt self-rescue whenever possible by swimming for safety. Be prepared to assist others who may come to your aid.

When swimming in shallow or obstructed rapids, lie on your back with feet held high and pointed downstream. Do not attempt to stand in fast moving water; if your foot wedges on the bottom, fast water will push you under and keep you there. get to slow or very shallow water before attempting to stand or walk. Look ahead! Avoid possible pinning situations including undercut rocks, strainers, downed trees, holes, and other dangers by swimming away from them.

If the rapids are deep and powerful, roll over onto your stomach and swim aggressively for shore. watch for eddies and slackwater and use them to get out of the current. Strong swimmers can effect a powerful upstream ferry and get to shore fast. If the shores are obstructed with strainers or under cut rocks, however, it is safer to “ride the rapid out” until a safer escape can be found.

If others spill and swim, go after the boaters first. Rescue boats and equipment only if this can be done safely. While participants are encouraged (but not obligated) to assist one another to the best of their ability, they should do so only if they can, in their judgment, do so safely. The first duty of a rescuer is not to compound the problem by becoming another victim.

The use of rescue lines requires training; uninformed use may cause injury. Never tie yourself into either end of a line without a reliable quick-release system. Have a knife handy to deal with unexpected entanglement. Learn to place set lines effectively, to throw accurately, to belay effectively, and to properly handle a rope thrown to you.