All that water and where to begin. Once again the best thing an angler can do is to diligently research the patterns of the species he or she is after. Fish follow patterns. However, come spring, when the water temps reach the low fifities, you can expect an upstream spawning migration. If you are fishing a reservoir, that puts the fish in a pretty confined area.
Incoming tributaries have the same effect on migrating fish.
An astute angler recognizes that this same pattern also holds true for walleye earlier in the year, and again for catfish later on during the year. Indeed most fish in reservoirs do make an upstream migration at some point in time during the year, so this is a general pattern that can put you on fish. Combine that with the knowledge that they also follow huge schools of shad throughout the body of a reservoir can make finding them even more difficult. Plain and simple. If you know the structural elements your intended quarry prefers, that puts you at an advantage.