A lot of people have never fished for Trout during the Winter months. The Truckee (Ca), and Little Truckee have been opened year round for three years now. I first seriously started Winter fishing when we move down to Reno about six years ago. The Truckee River in Nevada is a great Winter fishery. I have learned a lot since then and spend most of my fishing time in Winter mostly because I am to busy in the Summer and because I love the solitude. Be prepared to get skunked at first, but the fish you do catch in Winter are usually much bigger than the ones in Summer. Here's five simple rules.
#1 Do not fish the same type water you would in the Summer. Winter fish are lethargic, they will not move far to chase a fly.
#2 Do not start at the break of dawn. Water temps are cold in the morning and fish will not get active until the sun penetrates the water and warms the temp some. Winter fish like areas with little current. Look for current that moves like a slow walking pace.
#3 Patience is key. It might take a ton of drifts to get that fish to move on your fly. Instead of changing your flies all the time, work on getting good drifts. Same rule actually applies in the Summer also.
#4 Have a midge box. Winter trout eat midges, period.
#5 Fish during warm fronts. The Sierras are blessed with bright sunny days and high pressure even in Winter. Fish on days that are the warmest and get out a few days after a big storm when the water clears.