Once the troll and lure are in the water and working properly, you must then find the fish. Most lakes stratify into three layers during late spring, staying that way until late fall. The middle layer of water, the thermocline, contains both a large amount of dissolved oxygen and forage fish. To be most effective, you should troll close to or in the thermocline. This will be from 15 to 50 feet down in most lakes.
All fish relate one way or another to structure, shelter or cover.
They use it for protection from predators, to escape from direct sunlight, for feeding and, in some cases, for spawning. Deep water, docks or other man-made structure, overhanging trees, shade, underwater rocks, and cliff areas are all likely to attract and hold fish. Trout must have shelter, both from predators and from direct sunlight, so they always will be either next to or within easy reach of a shelter, cover or structure area. Locate food sources in a given lake, and fish will be found nearby. Minnows, salamanders, crayfish, midges, surface insects, beetles and other such creatures make up a large part of a trout's diet.