CONTROL
Control is essential to be able to detect strikes within an instant and quickly react to them. It is quite simple. If you have less control over your line and fly, you’re never going to be able to tell when a fish took your fly. More than often, takes are too soft to notice.SLIGHT BOW
Too much unmanageable slack is a bad thing. Slack is much like cholesterol, there is a good and a bad. Manageable slack is good – I’m sure a few doctors might agree, as well. Having too much unmanageable slack is another way of saying “you’re fishing blind.” There will be no indication of a fish take.
When you’re euro-nymphing or tight-line nymphing, the ideal amount of slack is a slight ‘bow’ in your line. If a fish takes, this slight bow will ‘tick’ and just ever so faintly tighten up. That is when you set the hook.
George Daniels likes to leave 1/2 inch tags, or "bunny ears", of the sighting material to make it easier to see the line tighten up. Now, you don't have to use fancy bi-colored sighting material. You can certainly use your normal leader or tippet as an indicator, but it truly does make a difference for visibility in difficult lighting.