Soon to begin my second season on rivers. I've fished dozens and dozens of them over the years but never seriously-just for fun-a diversion from loughs, lakes and puddles. Had my successes especially with sea trout. But never took the time to learn properly

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Well, I'm ready to now. I've heard many diff ideas regarding dry fly leader set up. I'm very aware that leader/tippet floating on the surface is a big no-no. But how close to the fly do you use sinkant? I heard let the last inch float, de-grease up to 3" away, sink all of it...so what is the best thing to do?
I typically fish on the edge of a riffle, rarely bother with flat featureless stretches, even if I see fish there. Also, I only fish small rivers, usually no wider than 10-15 metres, often narrower. A 9' tapered leader would be my usual choice, fly tied directly on the thin end. I try this and that with my leader set up but can't seem to settle on a standard starting place.
Any advice would be greatly appreciated...
Chris.