How far should you lead a rising trout?

One of the most common mistakes I ran across back in my days as a fly fishing guide on the Henry’s Fork, the Yellowstone and the Madison — as well as one of the more regular problems I see when I’m teaching at the School of Trout — is that most anglers have no idea how far to lead a rising fish with their dry fly. So why does that matter, and how can we increase our odds for success?’’