Like so many discoveries in fly fishing the first time it occurred was probably an accident. The observation was this; when your Elk Hair Caddis swung and flitted at the end of it dead drift, it got hit hard. And that leads a fly fisher to thinking, imparting movement on your dry fly leads to more hits. Skating is the term often used; Goddard Caddis is excellent at skating. But how does one impart movement and achieve a realistic float? There are some tricks.
The very easiest way to begin to get the knack for this is to simply cast downstream. As with all fly fishing strategies, placing yourself in relation to where the fish are is the first crucial step. So when beginning to learn this technique place yourself upstream from where the trout are working. After casting downstream shake back and forth some small ‘S’ curves to get some slack. Those curves are your coils of slack to work with. When the fly arrives over the trout, twitch your rod, the lighter the better, until your fly has the twittering action of a real one. Just one skitter is enough, about an inch or so upstream. And then let the drift continue.
Once you get the hang of it you can use curve casts or even simple mending techniques for across stream casts, to get some slack in your line and using the twitch when the fly enters to the feeding lanes.
One twitch in the slack and then a natural drift is all you need to increase strikes with your favorite dry caddis imitations.