Set your mower as high as possible. This allows the grass to grow higher and shade the weeds that compete for sun. This also allows the soil to retain moisture better, so less overall watering is required. Mowing the grass short promotes rapid growth, as the blade area is needed to provide sugar to the roots. Watering infrequently promotes deeper root growth and favors grass over weeds which typically have shallower roots. Water only when the grass shows signs of stress and do not water too deeply, as it can wash away nutrients in shallow soil. Fertilize with organic fertilizer in the spring and fall. Avoid chemical fertilizers, since they are typically salty and drive away the worms that aerate the soil and add nutrients.