Good practice when operating catch and release is crucial. If this is not undertaken then there is little point. There are guidelines, which, if followed, will ensure little if any disruption or damage to the quarry.
The Guidelines are:

Use barbless – de-barbed hooks wherever possible. (I am on record as to preferring micro-barbs for various reasons – not least infection reduction.) But if you are new to the game of C&R, then non-barbed hooks is the way to go.   

I tend, when operating C&R, not to use a net. There is more fish damage through careless use of nets than almost any other item.

Wherever possible, release the quarry whilst still in the water: this is why – if I am using barbless hooks – I use the rod-tip release method; the rod turning into an elongated disgorger; great for high banks and speedy releases. Do NOT do this is if you are not experienced!

If you do need to land a fish, do not grip with dry hands (always ensure that your hands are wet before handling fish – they are cold blooded, you are hot: not a winning partnership) or towel, both can damage delicate membrane, scales and protective mucus.

Never squeeze the fish.

Try to release the quarry over water; if it happens to fall, then it does so back into the water.

If a fish is a little “lively”, turn it upside down, so that the belly is facing uppermost; this will pacify the quarry and allow for easier hook release.
Be mindful of hot conditions and oxygen depletion: if I am fishing a lake during such times, I will not practice catch and release. OK on rivers; you can find a “push” of current to revive the fish.

Never overly-play the fish; land it sooner rather than later – if it gets off? You were returning it anyway.  

Don’t use catch and release to pay the number’s game. That is bad practice.  

When returning a tired fish, hold it against a current and wait until it “kicks” out of your hands. Always wait and ensure that fish has swum away strongly and not dived and started to suffocate in weeds.

Remember trout (and other fish) can drown. Desist from any practice that closes the gills. It needs to open and shut to survive, just like you taking gulps of air and exhaling.

Put the well-being of your quarry before anything else – including trophy photographs.