In the summer ol' marble eyes can be almost anywhere. First of all, note the water clarity. If the lakes you re on have dirty or stained water, the fish could be over shallow humps or points. If, on the other hand, the water is exceptionally clear, they could be located near deep sunken islands or deeper points. Usually though, on most lakes I'll begin my searching for walleyes on the weedline.
Walleyes use the weedline more than many anglers think.
Backtroll the weedline quickly, in search for active fish. The fisherman running the motor might want to try a live bait rig, while the other angler tosses a jig with a leech up into the weeds a little ways. Using this method you can cover a pretty wide area of the weedline. Vary the depth and speed of your backtrolling approach. If you don't find any biters on the weedline, try the points, flats, and sunken islands.