Eliminate, do not explore
Start at the most obvious transition you can find: a point, a creek mouth, the outside edge of vegetation. Fish it fast with something that covers water.
If nothing responds in fifteen minutes, leave. You are not fishing it wrong. There is nothing there.
Change depth before you change baits
Most anglers cycle through a tackle box while standing in the wrong six feet of water. Move vertically first.
When you find one
Stop and work it thoroughly. Fish of the same size are almost always together, doing the same thing, at the same depth.