[header] How to kill weeds [title] Determine the ideal height of your grass. [step] All lawns have an ideal grass height that promotes healthy growth. Depending on climate and geography, your ideal grass height is between 1/4 inch (0.635 cm) and 3 inches (7.62 cm). 
[substeps] Talk to a landscaping expert or a professional at your local home and garden retailer to get an understanding of the type of grass you have and how high it should grow. Keep grass a little bit longer when in doubt.