Buy a mower that has a “kill switch” built into the handle, so that when you release the handle, the engine stops and the mower stops moving.
There are sensible age limits for mowers. To use a riding mower, you ought to be at least 16 years old. For regular, walking mowers, 12 years old.
Wear strong shoes or boots, not flip-flops or sneakers.
Pick up rocks, sticks, pinecones, and toys before mowing, even if you are using a mower that collects the clippings automatically.
Wear goggles or safety glasses, and wear hearing protection. Once you get used to protecting your hearing, you’ll be amazed at how annoyingly noisy a mower is when you aren’t wearing anything.
Don’t mow when other people are nearby.
Put gas in your edger and mower outside, and do it before you start, not during.
If you are going to remove or replace the blade, disconnect the spark plug first.
Turn off the mower and wait for the blade to stop spinning before you empty the grass catcher, unclog something from the blade or under the mower, or push the mower across rocks or gravel.