Depends on a lot of variables... there are general locations that hold fish, but depending on water height and temp they will hold in different spots of that general area. In the winter when you have high cold flows, often steelhead will hold in calmer, walking pace water with holding structure; like behind or in front of a rock or tree. In summer, with low warmer flows, steelhead are seeking oxygen rich water, i.e. riffles, white water, just above the riffles and tail outs.
Best thing to do is go to your fave river when it's REALLY low and look for holding structure. You'll soon find holes that you love to fish at a certain river level! I found a slot on the Alsea last year with the low water that steelhead were just stacked in.. since the water was so clear and low all around the area the fish thought they were safe in this spot.. Haha not anymore!