Since most tailwater rivers have few large insect types and infinitesimal numbers of small ones, it is especially important for these trout to hold in slower water to feed efficiently. They dine virtually all day, which is not always true on freestoners, and the trick is to put drag-free, deep, and likely offerings right before their noses on a fine tippet. This is helped along somewhat by the high population of fish and their being spread over wide zones of slower water. But there are areas of higher trout-holding potential, and these hinge upon reduced water flows and food abundance. Anywhere the water slows on a tailwater is a likely fish-holding zone.
Edge waters all hold some fish, and often a good number.
They don't need any cover in the traditional sense, either. Inside bends and especially where points of land transmit expansive ripple lines are prime locations. The trout will be in the ripple or eddy line, and on the bank side of it in slower, shallower water. If a good hatch or spinner fall is on, many rising fish are likely to be seen in these quarters. Nymphing such ripple lines and just to the bank side of them is a very likely tailwater choice.