That's a pretty broad question. What kind of fish are you chasing?
Fish will need places that meet their needs in terms of:
temperature and oxygen Preferred Water Temperatures
Water stratifies, forming layers of different temperatures. In lakes it's often a matter of finding the depth of the preferred temperature, and trying to match it up with contours of the lake bottom. For instance if you know that the temp for the fish you are chasing is 20 feet below the surface in a deep lake, see if you can find a contour edge or hump that comes off the bottom to 20 feet so that the bottom is right at the preferred temp
Food- not only stuff in the stream, but current seams, eddies and mouths of tributaries that carry it, drop offs or points of land in lakes, weed lines in ponds that serve as ambush points. Also look for signs of food, caddis stonefly cases on rocks, stuff buzzing around or on the water, minnows crayfish scooting around. And herons, egrets, king fishers, mergansers, osprey hanging around- although they may be your competition they're there because the fishing is good.
Cover- both as cover from predators and as cover to ambush prey. Undercut banks, water depth over knee high at least, shade trees, deep water along the outside of bends, weed beds in shallow lakes or spring creeks. And if you think of cover as places where food can be easily ambushed, base of water falls, below dams, plunge pools, slopes along rapid changes of depth.
Refuge from current- rocks, holes, blow downs, pools etc. Fish may dart out in fast water to nail things, but they won't generally hold in water faster than you can walk. There may be small depressions or rocks that show up as dips or humps in fast water that can offer a place for fish to hold in fast sections.
Look for the stuff that naturally catches your eye. Rocks, points of land jutting out into a lake, and breaks between different types of habitat or contours--- where a riffle dumps into a pool, where a shoal rises up out of a lake bottom, where a small brook enters a stream and stream/river and river/lake. Changes in bottom from gravel to cobble, rocky shoals in lakes.
If you were a fish where would you be?
PS There is a ton of info out there on reading water in streams, finding fish in lakes, learning different the different types of lakes ("oligotrophic" or deep water, glacier carved lakes usually with fast drop offs to deep water near shore vs "eutrophic" - shallow lakes with lots of weed beds and lilly pads) and different types of streams (spring fed vs "freestone") and preferred habitat for different species, so if you can be a little more specific we could probably point you to more info.