The Wooly Bugger is a favorite fly for trout anglers. It's a wet fly, so it's generally fished below the water's surface. Wooly Buggers are a type of streamer (a large artificial fly that is designed to resemble bait fish or other aquatic prey). Carrying a selection of Wooly Buggers in different sizes is a good idea.
Because the fly is fake, you have to fish it in a way that makes it come alive so trout will be attracted to it. The video below shows you how to fish with a Wooly Bugger.