Between the months of December and Febuary, the tributaries of the Squamish, upper Squamish and especially small creeks flowing into Howe Sound become the home of these scrappy fish, overwintering and feeding on almost anything resembling eggs and smaller fish.
In Febuary, March and April, the Lillooet system becomes the best place to fish them, using Salmon fry imitations and smaller streamer patterns. They are easy to locate, often using available wood cover to hide near in rivers. In lakes and rivers both, the fish can sometimes be feeding only a few feet from shore. In lakes near creek mouths, they often create quite a disturbance on the surface, gorging on salmon fry. Casting and stripping a Rolled Muddler to boiling fish can be one of the most exciting ways to fish them, especially as they form a wake behind your moving fly and smash it at your feet.
A 4-5 weight rod is usually sufficiant in most streams, but sometimes a 6wt is needed to punch out the line through wind to those fish feeding offshore, especially in lakes. Boats can be used, but often fishing from shore is quite effective. Floating lines are standard but intermediate and type 3 tips are sometimes used.
If your thinking of Fishing in the winter, try the elusive Sea-run Cutthroat.