You can adjust the deck height of your lawn mower in order to cut the grass higher or lower. Most lawn mowers have multiple height settings for you to choose from. If you set the mower higher, you will probably have to mow your lawn more frequently. A good rule to follow is the 1/3 Rule. Cut 1/3 of the total height of the grass each time you mow. So, if the grass is 3 inches tall, try to cut no more than the first top inch of the grass.
Disconnect the spark plug boot from the spark plug, typically located on the front of the engine. This will prevent the mower from accidentally starting while you raise the cutting height of the mower deck.
Locate the height-adjustment levers on each of the wheels. Depending on make and model, walk behind lawn mowers can have one, two, or four height-adjustment levers.
Unlatch each adjustment lever from the notch for its current height setting. Push each lever forward or backwards to raise the lawn mower's deck higher off the ground. Refer to your owner's manual for specific height adjustment directions.
Ensure each adjustment lever is secured in a new notch for the higher setting. Check that each lever is adjusted equally to the same height setting.