Instead of a clean "scissor cut", a rotary-mower "whacks" the grass blade off.   Therefore, it is especially important to keep rotary mower blades very sharp.  Remember to balance the blade if you sharpen it yourself.

"Mow grass in the coolest part of the day for the cleanest cut."
Grass blades are more turgid when they aren't under heat stress (Example: summer afternoons).  However, dew interferes with good early-morning mowing, especially if you are mulching your clippings, so evenings are usually best.  Also remember that "wet grass conditions" will aid in the spread of turfgrass disease pathogens that are already present on your lawn.

"The longer the grass, the deeper the root." 
This saying reminds us to cut turfgrass at the highest setting possible.   2-1/2 to 3 inches is the ideal height for most home lawns.  Grass growing in the shade needs to be cut as long as possible, since it needs more leaf area to intercept limited light.

"Never remove more than 1/3 of the height of the grass at a time." (Example: If you are mowing your lawn at 3 inches, always cut it before it gets beyond 4-1/2 inches in height)

Mulching your clippings helps return nutrients to the soil.  Try to mow often enough, and under the right conditions, so that clumps of grass aren't left on the lawn.  Under "thick thatch" conditions it is probably advisable to bag your clippings.  Clean your mower deck after mowing.

Don't refuel mowing equipment on the lawn in case there is a spill.

Ensure your grass is cut short enough (but not scalped) to prevent it from "laying over" under deep snow cover. A 2 to 2-1/2 inch cutting height should be sufficient. It's actually best to gradually lower your cutting height over the final three cuts of the year, instead of trying to do it all in one final cut. Shorter grass is less likely to suffer from snow mold disease.

Check for any last minute leaf accumulations that may smother your grass.

If your lawn soil test calls for lime, late Fall is considered the best time of year to make a lime application. Retest your lawn soil every three to five years for deficiencies.

Late Fall is the time to apply "winterizer" fertilizers -- these are usually high in potassium, which helps winter hardiness and disease prevention. Even though top growth of your lawn has ceased, the roots remain active to "pick up" the nutrients. If you're applying both lime and fertilizer, it's best to separate the applications by two weeks.

After the final cut, service your lawnmower: Add fuel stabilizer to the gas tank and run the engine for 5 minutes to stabilize the fuel system (better yet... follow this step by draining the fuel tank and the carburetor). Perform all scheduled lawnmower maintenance such as oil change and lube, cleaning the air filter, replacing worn out or damaged parts and sharpening the blade(s). This is also a good time to install a new spark plug.