Pay attention to loons during the winter months they will give the fish away! They eat the same bait fish as trout and will help you lock in on smaller areas within a large flat. Here is a quick example... 

About a month ago Compton and I pulled up to a large mud flat with scattered shell. I knew the fish were in the general location but it is a large area. We waded for about 20 min without a bite. I could see several looms diving down and coming back up about 150 yards away. I quickly picked him up and moved down. As soon as we got out in front of the loons we started catching fish.