Sheeze, that's a big question. If you are in the Calgary area, hit Troutfitters (on Crowchild across from McMahon Stadium). They'll tell ya the best flies to get.
Stay the hell away from the Bow right now though (and alot of the South streams)! She is high, murky and fast. Probably at least a month away from starting to get ready.
Otherwise, learn how to cast and gently place your line accurately. The ability to read streams will come with time. It can sort of be taught, but every style is different, and every flyfisherman can catch fish in places that others can't. Strange thing, but it's the nature of the beast.
For instance, I've had some of my best sucess heading DOWNSTREAM and fishing nymphs by stripping against the current (no sh*t). Very small streams though.
Good luck, take everything you hear with a 'grain of salt' and learn for yourself. Casting is everything, and then it's entamology..........
Tree