The trout, particularly the large ones, are well educated and can be picky. It pays to get the latest info about successful flies and techniques by talking to the people who work in the fly shops. Both Park City and Heber City have excellent shops with knowledgeable employees.
Information can be found at http://wildlife.utah.gov/index.php
Jordanelle Reservoir is one of Utah's most popular flatwaters. It offers trout, smallmouth bass and perch. Nearby, Rockport Reservoir is usually good for these same species. Trout fishing is good year-round, whenever these reservoirs have open water or ice that is solid enough to walk on. Trout taken from shore or boat by anglers fishing baits (Powerbait or worms) and small lures. Bass are taken using jigs and crainbaits. Perch will bite virtually any small bait.
The Uinta Mountains to the east offer hundreds of small lakes and streams teaming with trout. These mountains are all but inaccessible during the winter because of deep snow and extremely cold temperatures. The mountains begin to open up during late June, and snow may shut down the high passes in late September. The growing season is short here and so trout are usually small, but they are almost always hungry. Fishing can be very fast.
Strawberry Reservoir is not far from Park City and it is Utah's most popular fishing water. It is usually good for large cutthroat and rainbow trout and kokanee salmon.