An entire book could be written on covering water, but I'll include a few basic tips here. In general, I find it easiest to work from shallow to deep, whether trying to find bass, pike, lake trout, perch or whatever. Shallower water is usually much easier to fish/cover. There are plenty of exceptions to the rule - e.g. shallow water bass fishing in the summer after a very cold night is often a waste of time, but day-in and day-out, working shallow to deep is easier for me. So if I'm pike fishing on an unfamiliar body of water, once I find a good looking area I may start casting in 5' to 10' of water with a spinnerbait, rat-L-trap or jerkbait. Then maybe move out to 8' to 15' and so on. I try to stick with lures that I can work quickly (like a swimbait) until I determine that I need to slow down.
With lake trout jigging, during most of the year this "shallow to deep strategy" pays off. But in the middle of winter into April/May, the deeper water is often worth a look before spending too much time shallow. Many anglers make the mistake of staying shallow for lakers in April, just because they catch one or two. There will almost always be some shallow fish around somewhere, but in alewife driven fisheries the deeper water usually holds the majority of fish in the early spring. And sometimes the fish are deeper than you think. In April and early May, Canandaigua Lake's lake trout are often concentrated in around 200' or more water from what I've heard. I'm going to try some deep techniques out there this spring if I can make it out there.
Re: Lakers - Things get tricky once the thermocline sets up. A 10' to 20' change in depth can make a world of difference. I've learned that the hard way on more than one occasion!
If you're on a new body of water, or fishing a new area on a familiar waterway, it can pay big dividends to cruise around a bit checking things out before wetting a line. Don't just start fishing without knowing what's around the bend! I try to study maps, ask around and do some homework before I reach the lake/river. Sanders Fishing Guides were invaluable resources for me - and they still are. Patience is only a virtue if you know the fishery! Sitting in a bad area all day long not catching fish is no virtue! I'll sit on an area if I'm sure it's my best or only option and I have a hunch that the fish will turn on. Usually there are better opportunities if things aren't hitting.