Some of my thoughts on the matter to assist the newer fly fisherman...
First the obvious - hands wet at all times when handling fish. The slime on a trout is it's protective barrier. Dry hands, grass, dirt, hot rocks, etc.. that come in contact with the flesh is bad...
Bring the fish in quickly. A small or large fish can usually, barring certain conditions, be brought in more quickly than they usually do. Two reasons come to mind on why people play the fish out too long:
1)You haven't caught a fish in a long while and want to "play" the fish or you just want to see the fish do multiple runs and watch your line go out hoping you get to say "he took me to the backing a few times" Legit, awesome! but knowing your drag helps..
2) Know the limitations of your tippet. Use the largest tippet (and strongest tippet - I swear by Frog Hair for invisibility on the FC, suppleness, knot holding superiority and diameter to strength ratio ) for the conditions.
Again, you can get the fish to net quicker, thus not exhausting the fish and possible aftershock issues and lost fish with flies and tippet swimming around afterwards.
Fish in the water as much as possible, pics are cool, we all enjoy seeing them, but most of the staged shots with the fish in front of the fisherman and the shot taken by the friend end up out of the water much longer than what was originally intended, no? We all make mistakes when we try to capture the "big one" and that is to be expected but keep the photos to a minimum and fish pics more in the water/underwater.. Don't be obsessed with thinking you have to capture all your fish. Very rare circumstances are we in a position to get a photo of the "fish of the trip" anyways.
Barbless hooks, always. Very little difference the barb on a small fly makes anyways. If you keep the pressure on and rod tip up you will keep your fish. Either tie or by barbless or use the hemos to bend back the barb prior to using.
I am looking into a hook remover such as the ketchum release that fly addict provided the link to. Most flies I can get out no problem by grabbing near the eyelet or shank of the fly or using hemostats to grab the fly shank but my recent trip to the San Juan River, NM where you are using micro midges, it was very difficult to remove as the flies were so small #24 - #28 as even a small hemostat was too big. If someone has a solution please let me know as I am always looking to learn better techniques...
Warmer 70+ water temps make trout more lethargic and recovery time for the fish is much longer. Kinda like we feel going climbing out of a canyon on a hot summer day....
Nets. Carry one always so you can land and properly remove the hook and spend the extra money for one with the "ghost" style net material or similar. Better for contact with the fish and virtually no issues with getting your fly tangled and hooked in the net material. They sell the netting separately and you could make your own out of saplings, better yet step up and support Greg and custom order the most beautiful and finest nets available!
http://www.sierra-nets.com (shameless plug
)
When all possible release the fish gently. If a fish is lethargic when you go to release it or it turns on it's side, you need to hold the fish up and get some water flowing into its gills. back and forth. A fish that rolls on it's side means it's air bladder is empty and needs to be filled. This is how a fish maintains its equilibrium and stays upright. Again, wait till the fish can swim away normally on its own...
Most all of these suggestions have been discussed many times but if you are practicing catch and release, Photos and over handling fish I think are the biggest culprits. We all like to remember our fish but please keep it to a minimum and when the timing is not right to take that shot because you or your friend is 50 yards away forgo the shot and you will have the fish for life in your memories.....