Safety

According to the American Association of Orthopedic Surgeons' 2006 data, over 100,000 people in the United States suffered an injury in a lawn mower accident for that year. Some of the most common injuries are due to slipping behind and under the lawn mower on wet slippery grass (yikes), or overturning a lawnmower on a steep hill. Most lawn mower injuries are preventable if some basic safety guidelines are followed.
Wear protective clothing such as goggles, gloves, boots and long pants, and never, ever, mow barefoot or in sandals!
Have your lawn mower serviced before the start of the season to ensure it's working properly.
Do not remove any safety devices on the machine!
Be sure to add fuel before starting the engine, not when it's running or hot. The liquid could overflow and flame up.
Keep hands and feet away from the lawn mower blade even if the machine is turned off. Once cleared of an obstruction, a blade can swing around and cause injury.
Consider Kevlar-filament chaps (when using a chainsaw) that are designed to tangle into the chainsaw chain on contact and stop the saw in a fraction of a second as opposed to cutting into your leg.
Don't forget the hearing protection.