Tapering a leader is a very good idea, especially when fishing in calm conditions where there is very little or no wind to help turn the fly over. Tapered leaders also offer very good presentation, which is essential for river fishing.

You can either purchase ready-made knotless leaders (such as the ones from Rio), or you can make your own. For example when fishing with lures I will start out with a 5ft butt section (the part of the leader which is attached to the fly line, either through a braided loop, nail knot or a welded loop on the fly line) of 10lb Fluorocarbon, using three-turn water knots I will attach to this another 5ft section, this time 8lb fluorcarbon. Finally I tie on another 5ft section using 6lb fluorocarbon. I use this set-up when fishing wets, nymphs and lures however you can change the leader material, leader length and the breaking strain to suit the conditions and your quarry. Remember to always lubricate your knots with sailva before pulling the  tight.