Kill the Weeds in the Lawn, Not the Grass. How to controll Clover, dandelions, and Crab Grass.

The best way to keep your lawn weed free and green is by daily care. Spray your lawn in early spring, again in late spring, and spot spray as needed.
I use Spectracide, but the Ortho spray works great as well. I do not use Scott's brand weed and feed because it is pretty expensive compared to the generics (but Scott's is GREAT stuff). Clover is a bitch, it is extremely hard to kill. Crabgrass must be controlled before it germinates. Crab grass emerges when the soil stays at about 55F for about 5 straight days. Apply crabgrass controller before the 5 straight days of 55F (in the Midwest, generally apply about April 5th). Weeds will overtake the lawn if you do not pay attention. When the weather starts to get hot, the grass will not grow very much but the weeds will suck up all the water in the soil and take over. Choke out the weeds by developing a thick lawn. Fertilizer is the key to a great looking lawn. I buy cheap fertilizer at Lowes, Home Depot, or Menards (any hardware store/Wal-mart). I use a broadcast spreader to apply the granules. Dandelions emerge early and are easily controlled, just don't kill the flowers and shrubs. Clover will spread quickly and is hard to kill. Your yard is an indication of how proud you are of your home, take good care of it.