The best place to fish a lake with full of muddy water is to find the clearest water on it. Often the creeks near the dam are a little less muddy than others. Some big lakes almost always have clearer water near the dam and smaller lakes may have water a little better. Ride around and find the clearest water you can.
If the water is muddy everywhere, there are some options. Fish gotta eat even in the mud, and they are able to find food. After all, a bass can find a black plastic worm on a dark night and a crappie will eat minnows at night, so they don't have to see them. They do react by holding closer to cover and don't chase food as far though.
If the lake or river is extremely muddy you can improve you odds by fishing a bait that makes noise. A plug with rattles in it give the fish something to zero in on. Rat-L-Traps are made to make noise and Mann's Loudmouth, like other diving crankbaits with rattles, all help the fish find them. Give the fish a better chance to locate the lure by fishing them slowly and steadily. Although I usually fish a plug with a stop and go motion to imitate a easy meal, in muddy water I like to reel it steadily so the bass can track it.
Rattles on jigs like the Rippler and the Rattle Back are good when crawling a bait on the bottom. You can also get rattles from Zoom and other companies to add to the trailer or insert into a plastic worm. You can add beads between the lead and worm on a Texas rig or between the lead and swivel on a Carolina rig to click when you shake the rod tip. When fishing these baits, move them as slowly as possible and shake your rod tip to make them sound off.
A spinnerbait is also a good choice for muddy water. The spinning blade sends out vibrations the bass can track. Some have rattles or you can add them. Choose a bait with a Colorado or Indiana blade rather than a willowleaf for more vibration. Some spinnerbaits have blades made for making more noise. Again, move a spinnerbait consistently to offer a easier target.
For bass and crappie, and probably other fish, color makes a difference. Crappie jigs usually don't have rattles but you can choose a color they can locate easier. Black, chartreuse or red all show up and combinations of those colors seem to be good in muddy water. One of my best crappie jigs in muddy water has a red head, black body and chartreuse tail.
I like chartreuse spinnerbaits or crankbaits in muddy water for bass. I usually use a black jig and pig with some chartreuse strands in the skirt. Bright blue also works in muddy water and Chris Baxter with Zoom swears by a black and blue jig with a sapphire blue Super Salt Chunk trailer for muddy water.
After saying all that, the muddy water probably affects the fisherman more than it does the fish. Adjust your attitude and realize the fish can find food in the muddy water. Then help them out a little by choosing the right bait, fishing slow and steady, and you should be able to catch them. The worst thing you can do is stay home because the lake is muddy. Fishing muddy water is much better than not fishing!