Water your lawn weekly instead of every day. This will encourage deep root growth which means stronger grass and less room for weeds.
Water your grass early in the morning so it has dried by nightfall. Fungus thrives at night, especially in wet grass.
Set your lawn mower blades to a height of three inches so you can get rid of weeds but not disrupt the roots of the grass. Check that the blades are sharp, as dull blades can rip the grass and weaken it.
Mulch the grass clippings in the yard instead of having them collected in a bag or raking them up. The clippings will decompose and release nutrients back into the soil.
Add clover to your yard or avoid mowing it if it grows there naturally. This may sound backwards, but clover is actually a good weed that adds nitrogen to the soil
Get rid of weeds by spraying them with undiluted vinegar.
Spread corn gluten on the lawn in the spring. This will prevent dandelions and crabgrass from growing, and will make the grass stronger.
Clean up dog poop as often as possible, as too much of it can kill the grass.
Have a soil test done if your grass is dying or looks weak. This way you will know what nutrients your grass is lacking so you can remedy the problem.