I love winter fishing, it's awesome, probably my favorite time. Throw in some snow and I can't wait. Here are some things that I've learned through the years.
1. Have a good layered clothing system and get two of each. Keep the second set in the vehicle. Layers are so important, you need to be able to adjust, I can get pretty hot even on the cold days.
2. If you fish alot in the winter get some boots that are a size too big so you can wear two warm socks. If your feet sweat get a thin polypropylene sock liner to wick the moisture away.
3. Have handwarmers, if your hands are really cold secure them to your wrist where the blood flows, this is a miracle for people with cold hands.
4. I fish junk flies and midges in the winter with the occasional dead drifted bugger. Find the slowest water that is seamed up with quicker currents, these are the magic winter spots.
5. Travel less but pick the areas that meet the above criteria hard. Don't be afraid to go back and fish it again with two new flies. I don't cover nearly the amount of water I would in the other seasons.
6. Make weight adjustments and don't be afraid to experiment. If I'm not catching fish I add weight, if the fly is moving too slow I can always lead it. A fly that is moving quick in the winter rarely catches fish.
7. This is a bonus, not always possible but find water that is slightly warmer, think tailwater or spring fed. The closer I am to that warmer water source the better. The difference between water that is 41 vs 39 is a hell of alot more than 2 degrees.
8. Get into a good rhythm if guides are freezing, cast, drift, swing and dunk so the water gets rid of the ice. Then repeat.
9. Last thing, don't be afraid to go early. Yes it's colder but I've had some fantastic times at first light in the winter.
good luck, post a report and have fun!