Returning fish alive is not as simple as it sounds. There are ways of handling fish that can kill them. Follow these steps to insure the best chance of survival for the fish.
Fish MUST be released (all river and stream fishing) alive immediately in the same water where they were caught.
Please put them back ALIVE!
Do not "play" the fish to exhaustion.
Keep fish in the water as much as possible when handling and removing the hook.
Make sure to wet your hands before handling the fish. Dry hands can take off the slime coat - this coat prevents the fish from contracting infectious diseases.
Remove the hook gently, don't squeeze the fish or place your fingers in the fish's gills.
If deeply hooked, cut the line, do not remove by pulling out.
Release the fish only after it's equilibrium is recovered. If necessary, gently hold the fish facing upstream and slowly move it back and forth. Release the fish in quiet water.
If you are fishing in catch and release waters, strongly consider crimping the barbs on the hook or you can buy barbless hooks.
If you are not familiar with Catch & Release techniques here is a great article we found online written by Rick Schroeder: http://www.coloradomountainfishing.com/trouthandling.html. It's great to be informed so we can keep our fisheries as stellar as possible!