If a few weeds have popped up in your yard, you might be able to pull them up from the roots by hand.
But for a serious weed problem, you might need an herbicide.
Be sure to use a product designed for the species of weeds and their stage of development.
To prevent weeds from taking root, water your lawn deeply and infrequently.
Use fertilizer, and keep the grass fairly high so weeds don’t get enough sunlight to grow.
If you have had weeds in the past, use a pre-emergent herbicide to keep them from coming back.
Employees at your local garden center can provide helpful advice.