Hi,
I've caught, kept, and cooked a few in my time, but it has been a long time. I heartily endorse C&R.
With that said, first, stocked fish are not that tasty. Trout stocked at 8-9 inches would be better left in the water till they reach 10-12 inches. Older, larger trout DO get a fishy flavor, and if you like that, it's fine. Clean them out, removing the entrails and the dark line along the backbone. Trout should be cooked with their heads on as you can lift them carefully by the tail and with a butter knife,gently peel the fillet from one side, then the other AFTER THEY ARE COOKED.
Trout are best cooked fresh, fried in bacon fat, till they are tender-white inside. Salt and pepper, perhaps some lemon juice, and you've got a decent meal.
Most fly fishermen would be outraged at the thought of killing, cooking and eating any trout, however, taking one or two for the table would not be so terrible, IMHO, however do not kill fish you do not have any intentions of eating. That would be a waste. Take only what you know you WILL eat.
I know many trout fishermen that catch and catch and kill all they catch and they can not possibly eat them all. They go to waste in the freezer. That is something I can not endorse.
Mark
PS-If you like eating fish, Freshwater Perch are much better than stocked Trout, again-IMHO. You need to know how to fillet them, but covered milk, flour, egg, then with breadcrumbs and fried, they are superb-better than trout any day.
"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt
Flymphs, Soft-hackles and Spiders: http://www.troutnut.com/libstudio/FS&S/index.html