1. Cut no more than 1/3 the height of the grass.
2. Never scalp the lawn or cut below plant crowns.
3. Mow only when the grass is dry.
4. Change mowing patterns frequently to prevent compaction.
5. Leave clippings on the lawn unless they are very long or wet.
6. Mow with a sharp blade. Resharpen after every 10 hours of use. Bring the blade to a professional sharpening service once a year. Replace the blade as necessary.
7. Rinse clippings off your mower after it has cooled to reduce the chance of spreading lawn disease.
8. Cut grass at the high end of the recommended height range during hot weather.
9. Cut at the low end of the recommended height range during cool weather or in shade.
10. Make your last cut of season at the low end of recommended height range.
The Right Height
There are several reasons not to cut your grass too short. First, grass grows from the crown, not the blade tips. This trait makes grass ideal for lawns because it keeps on growing despite the regular mowing off of its upper stem, leaf sheath, and blades. This is also why it's important not to damage grass crowns by accidental scalping with the mower. No crown, no grass! Second, keeping grass on the longer side allows it greater surface area to carry out photosynthesis. This in turn results in healthier plants. Third, taller grass grows slower than shorter grass. You can use this simple fact to eliminate up to 20 percent of the mowing you do annually. That's a saving of about 8 hours a year for the average lawn owner, not to mention the savings of gasoline and wear on equipment. Lastly, by keeping your grass at the upper end of its recommended mowing height, you can prevent most weeds from germinating--and thereby eliminate the need for herbicides.
When to Mow
Most cool-season grasses should be cut when they reach heights of 3 to 3-1/2 inches, typically once a week. Cut warm-season grasses when they reach 2 to 2-1/2 inches. Cut no more than 1/3 of the grass height at each mowing to avoid damaging the plants. If the lawn grows too high for you to cut off 1/3 the height and have an acceptable length, cut off one-third now and mow 1/3 off again in two or three days. Cutting more than 1/3 the height results in clumps of clippings that tend to lie on top of the lawn, decompose more slowly, and give the grass a less attractive, open, bristly appearance. In addition, short cutting will stunt or slow root grow and weaken the grass plants.
Article courtesy of yardcare.com