Leave the mower on a higher setting; i.e. not cutting grass very short each cut
The idea that the shorter you cut your grass, the less you have to cut it, is flawed. Grass that is cut too short leads to weed invasion and drought/heat damage. Generally, never remove more than 1/3rd of the grass blades during any one cutting. Allow for all grass to grow taller during the summer and if there is a drought.
Cut your lawn frequently; i.e. avoid ‘super long’ grass
During peak season, it is recommended cut your grass every 5-7 days. Grass that becomes too long is difficult to cut and creates more work because clippings have to be bagged or disposed of (instead of mulching them back in). Also, too long grass attracts weeds, bugs, and critters.
Alternate the pattern or direction in which you mow
Cutting in the same direction or pattern creates ruts in your yard. The soil compacts and can prevent grass from growing as well as it could.
Mow during the cooler part of the day and when grass is dry
Mowing lawn during the peak heat hours or when grass is wet can leave the lawn damaged, your mower clogged, or the lawn looking just plain sloppy.
Sharpen your mower blade
Just like any other blade, your lawnmower blade dulls over time. A dull blade results in a jagged cut on the blade of grass. This can lead to turf diseases and pests creeping in, as well as, a less green look to your grass. Have your blades sharpened at least once a year twice is recommended. It may be wise to have an extra blade on hand, so your lawn can always receive the best cut possible. Obviously, avoid mowing over branches, stones, or any other items that may further dull your blade.
Mulch your lawn when cutting
Allowing your grass clippings to go back into the lawn, instead of a bag, is commonly referred to as ‘mulching’ the lawn. It is very healthy for your lawn as long as the lawn has been cut frequently. The grass clippings help to fertilize and feed your lawn. It may be wise to purchase a mulching blade for your mower, so the pieces of grass are cut smaller.
Mow across hills, not up and down them
Even if a hill does not appear very steep, mowing across is advised for your safety.
Allow grass to grow longer in shady areas
Set your mower deck at a higher height for these areas. This will prevent the grass from dying off or having a shallow root base. It will allow the grass to catch more sunlight as well.
Add’l Source: DIY Network