Perchslayer, there is a very easy way to know what flies you should use. First of all no matter what stream, river or lake your fishing at. Do a bit of research and not just on a forum. Talk to your local fly fishing shop. Go to a meeting of you local fly fishing chapter. Like, Northern Fly Fishers, or the Hook and Hackle club. Talk to people who fish where you fish. Or where you would like to fish. Or take a lesson. Most fly shops offer lessons in casting, fly tying and entomology.
If it's trout your after and by your question you asked specifically about "wild trout". Don't look past stocked ponds and lakes with hatchery trout in them. They can give you some success and confidence when starting out. Confidence means not only in the fly that your using. But also in fly fishing in general. Too many people pick up a fly rod and expect that it will be easy to cast and easy to catch fish. Nothing worth while is ever easy.
Here is a link to all the ponds and lakes that were stocked in Alberta for 2013. For the most part the list remains the same each year.
http://mywildalberta.com/Fishing/Sto...s/Default.aspx
For what flies to use there is a very simple method. Find out what bugs live in and around the waters you want to fish. Be observant. Look around. See what kinds of bugs are flying around the area. See if any bugs are landing on the water your wanting to fish. Turn over some rocks near the edge of the water and see what is living on around and under them. Watch the water to see if there are any feeding trout, and look to see if you can see what they are feeding on. That will give you an idea of what flies to use and what color. You don't always have to "match the hatch" perfectly. Sometimes a close imitation will be good enough for a hungry trout. Wild trout and hatchery trout will both be just as eager to take a fly.
Good luck out there,
Tight lines.