FlyFishingPoint offers a great variety of information, here is an example of how to learn about the French nymph technique. But you can find a lot of other interesting stuff on this fabulous website.
On my fly-fishing journey, there have been a few milestones that resulted in raising my nymph fishing abilities to the next level. The first happened long ago on the Strela River, when I realized that I had left my fly rod at home and tried fly fishing with my friend's jigging rod. That was my first practical experience fishing the short nymph (since nothing else was possible with that set-up). The second experience was with the discovery of jig flies, when Jiri Klima demonstrated their killer effectiveness to me while fishing together in England - thanks to him I managed to catch nice brookies out of deep and fast currents where I previously wouldn't even have seen a fish. The third milestone came when I saw the small flies with tungsten heads being fished by Dan Svrcek, who at that time had caught many times more fish than I, in part due to these small but heavy patterns. The latest nymphing moment which brought me to the next level was my introduction to the secrets of fishing with the long French leader. There is a lot of talk about French nymphing these days, but it still not considered a standard fly fishing technique like the already classic Czech nymphing. In these few lines here, we'll take a closer look at this method of fishing with the French leader....... read it all here