Get the mowing height right for the right time of year.
There's more to mowing than just cutting the grass every saturday. One of the most fundamental steps to a perfect lawn is getting the mowing height right for your type of lawn and for the season.

Most grasses do best with a length of 2 - 3". This applies for spring and early fall. In the summer, if possible, set it even higher. Never go below the minimum recommended height except for the first mowing of the season which should be around 1.5" for most turf grasses.  Mowing it short once in the early spring will allow the lawn to green up quicker in the spring. 

Mowing height is important because the grass uses the extra length to absorb the sunshine it needs to grow and develop into a healthy plant.

Never remove more than 1/3 at any one mowing. This may mean you'll have to mow more often during prime growing times (usually spring and early fall).

Leave the clippings on the lawn after you mow. This not only save time and energy, but the clippings decompose and add vital nutrients back into the soil. Grass cycling recycles plant nutrients back into the soil. Clippings contain the same beneficial nitrogen, phosphorus and potassium nutrients as that expensive bag of fertilizer. In fact, clippings can provide up to one-third of the annual feeding requirement for your lawn.

Use a sharp blade.
The type of mower doesn't matter, but the blade's condition does. A dull blade tears at the grass. Take a close look at a grass blade a few days after mowing. If the blade is dull you'll notice a jagged brown line across the tip of the cut grass. This is a good indication that your blade needs sharpening. Professional mowers sharpen their blades about every 8 hours of use. For most homeowners, twice a year is recommended. The jagged edges caused by a dull mower blade make it more difficult for the grass to fight off pests and disease.