Following these tips will help your lawn become healthier and more sustainable:
Different types of grass have different optimal heights, but you should generally mow high. This means 3-3.5 inches for many types of grass. This allows for more root growth and also helps shade out weeds.
Only cut 1/3 of the length at a time. Cutting more than this will unnecessarily stress the grass. If the grass is allowed to grow to 6 inches, you should cut it down to 4 inches, and then wait a few days before cutting it to its regular height.