Purchase a selective herbicide that targets clover and similar weeds but doesn't take out your grass. You can also keep it from growing with corn meal gluten or remove clover from your lawn manually at the start of the season as part of your lawn maintenance checklist.

Johnsongrass and crabgrass are invasive weeds that can overtake your lawn. Crabgrass is a low-growing grass most often seen in lawns, flower beds, and vegetable gardens. While you may find Johnsongrass growing in your lawn, it will also grow in pastures, crop fields, and the edge of the road. Johnsongrass is much coarser than crabgrass. If left alone, Johnsongrass can grow up to 8 feet tall. 

Pulling weeds once per month is typically often enough to keep most weeds at bay. But in general, it's best to pull weeds as soon as you spot them to prevent deep root growth and slow their spread. To make it easier, plan your weed pulling after rain or after the sprinklers run so the soil will be nice and wet and the weeds will be easier to pull. If you notice moss accompanying weeds, make a plan to remove the moss immediately to prevent damage.

The fastest ways to kill weeds and unwanted grass include burning them, pouring boiling water on them, or pulling them out by hand, as these methods work almost instantaneously. For a quick-acting solution that works within a few hours, you can use a commercial-grade herbicide like glyphosate or a DIY vinegar, salt, and dish soap mixture. While effective, be aware that commercial herbicides introduce chemicals into your lawn. The slowest method for killing weeds is to starve them of sunlight and nutrients using mulch or fabric covers.