I leave for a trip tomorrow, so I have been daydreaming about this very topic at work all day...
I have tried many, more elaborate methods of cooking backcountry trout, but I always come back to the same simple method, partly because of the ease of preperation, partly due to the low weight of the ingredients, but mostly because I like it best.
I use a MSR Superfly stove since it has a somewhat large burner so I can get a good, dispersed heat along with a MSR Duralight 7.25" non-stick frypan with lid. I rarely have anything stick and the lid aids in quick cooking and steaming if desired. Unfortunatley, I had to buy the whole cookset in order to get the lid with the rest of the set going largely unused as I use titanium for most of my cooking.
The plan is pretty simple, heat a little olive oil and throw the fillets or, if small, whole cleaned trout in. I usually cut off the heads and tails due to my pan size. About midway through the cooking process, I drizzle about half a lemon juice packet (Coffee Bean) on the fillets or in the body cavity and add thyme, garlic powder, (and sometimes rosemary) along with a little salt and some fresh cracked pepper from my GSI pepper grinder. This is one of my luxury items I have grown to be unable to go on a trip without, along with my Snow Peak double wall titanium cup, but that's another story. I have used fresh garlic in the past and have found it burns easily and often overpowers all the others spices, so I stick with powder. It can be easily used to spice other meals as well. Anyway, let the trout cook until done and then add the remainder of the lemon juice just before serving.
It is dowright delicious and the natural trout taste shines through.
If your group has two or more stoves and frypans/pots, I have found that sauteeing up some almond slivers in butter (preferably) or oil and then adding some already rehydrated Mountain House green beans along with some salt makes a pretty good side dish. Fresh, pan-sauteed, herb trout with green beans almondine at 11,000 feet - Life is good. It's not neccessary, but on trips with the wife, I bring along a little Chardonnay and