Casting is crucial, sure. But what happens after your flies hit water—the presentation—is more important. You want to avoid the drag created by currents pulling on your line, which will cause your bugs to drift unnaturally. Mending, the lifting and placing of your fly line upstream from your flies, negates that problem. As a rule of thumb: Mend when your fly, or strike indicator, is even with your position in a run, and not before. And remember that one solid mend is always better than many halfhearted mends.
 Lift the Rod: The No. 1 mending mistake anglers make is trying to flick the line from a low-rod position. Fly rods are long for a reason. Use the full length of the rod to lift as much fly line as possible off the water before you start to mend (a).
 Sweep the Line: With the rod tip pointed toward the sky, sweep the line upstream (b). Do this with authority, but do not overpower the mend. A perfect mend moves all the fly line but does not jerk the fly or strike indicator as it rides in the current.
 Feed the Drift: Place the line back down on the water. To get a longer drift, you can “stack mend” by gently moving the rod tip up and down to flip and feed loose coils of line (c) through the rod as the current carries your fly downstream to the trout.