Try fishing the same locations that you might catch walleyes at. Take ATV, 2 anglers, drill 50 holes per spot in a grid, and if you don't mark any fish move to another spot. Continue to "ice troll" for the whole day. We have drilled upwards of 200 holes on Glendo in a day. It's not hard to figure out where Trogdor, 3lungs, and I had been fishing. During certain times of the season we would mark many fish, but could not get them to bite anything. You will run into that for certain.