A weed is a plant that is not wanted but succeeds where more desirable plants fail. A successful effort to remove broadleaf weeds from a lawn is a campaign rather than just one battle. Broadleaf weeds produce thousands of seeds per plant, while turf grass gets deadheaded every week. To make it worse, weeds like chicory and creeping Charlie flourish in drought, shade and infertile soil. The best way to remove them is by choking them out with healthy lawn grass.
Wield a dandelion digger with prejudice as soon as the first bloom appears. It's good exercise and it gets you outdoors. It also cuts down on the need for herbicides. Thick turf is the key to weed-resistant lawns; pulling early weeds gives grass a chance to grow during spring, when it grows fastest.
Over-seed sun-loving Kentucky bluegrass with a shade-tolerant variety like fine fescue under trees and where it will be shaded by buildings. Broadleaf weeds thrive in shade where turf is thin. Over-seed in fall so the grass will start growing in spring before the weeds start in early summer.
Mow your lawn to the right height; 2 to 3 inches is an average height. Some grasses' optimum height varies; tall fescue can be kept at 4 inches and Bermuda grass grows best at 1 to 1.5 inches. Keep grass a bit shorter in spring and longer in summer, but mow frequently enough that you never remove more than a third of the leaf at a time.
Water deeply, don't "sprinkle"; shallow weed roots grab surface water. Water infrequently but make sure that grass gets an inch of water a week. Use a rain gauge or sink a soup can into the lawn to measure the weekly total of rain and irrigation.
Fertilize lawns in fall for best results; in September or October and after the final mowing in October or November. Use a slow-release nitrogen fertilizer that provides two to four pounds of nitrogen per 1,000 square feet of lawn. Some weeds, like clover and medic, are giveaways to a nitrogen-starved lawn.
Apply herbicides only when needed and according to label directions. For general control, use a combination of herbicides: 2,4-D, MCPP (mecoprop), and dicamba in fall when perennial weeds are storing food or in late spring when annual weeds are germinating and actively growing. Spot-treat individual weeds with a spray if they refuse to die after digging.