For trout, I've had some of my best days in the winter and seem to have better luck with big flies in the winter. A #10 is the most common size fly for me this time of year, but #8,6,4 size flies are also a staple in my box right now. Dead drifting, and swinging them works very well. But I'd suggest using Buggers and BH nymphs. All of this info might be useful just in my area, but if you fish any mid size rivers, this might help.