Most people think that to catch a lake trout you have to fish the bottom. While this is true of where lake trout are much of the time, the most active lakers(the ones that are more likely to bite) are those that are suspended often at the thermocline. These fish are here because they are looking for bait fish which prefer the temp/oxygen levels found around the thermocline. I have found a fish finder to be a very helpful tool in fishing/trolling for lakers. Fish the depth at which you are marking fish. As far as not using downriggers, leadcore line works well for getting your lures to where the fish are. The colored line allows you to know what depth your lure is at. Also dipsy divers off of a linecounter reel are excelent, inexpensive ways to get lures deep. They come with a chart that tells you how much line to let out to fish the desired depth.