A nice visual for the beginner, to show/explain Riffles, Seams, the Bank, Joined Seams & Rocks importance in providing fish oxygen, feed and protection. Check out Generation Fly-Reading Water Effectively

Adam Reader on Reading Water (Generation Fly)

Nice visual and simple explanations re holding lies.

Also, a 2006 piece by Mike Gorman on where Steelhead like to hold at Gorman Fly Fishing

“….my assessment that more than 99% of the area in a typical river does not hold resting steelhead.  Most of any given river may be too shallow, too fast, too slow, too exposed, too warm, too cold for steelhead to linger for long.  The astute angler must discover the “Sweet 1%”.”