Don't build your house in a flood zone.If more people took that to heart we could avoid so much misery and expense.
Be sure you hit him hard the first time.If you are going to hit a person or an animal you then don't just play around. Make the first one count and you may not need a second one.
When you are buying a truck or a tractor always get one a little bigger and more powerful than you think you need.I would add that when you are buying a trailer you should probably get one with a higher load capacity than you think you need. The obvious exception to all this is if you will be using the truck, tractor, or trailer in tight places.
Don't put your foot under a lawn mower and disconnect the spark plug before you start to work on it.It sounds obvious but I hear of people being injured every year while working on a mower, power saw, or tractor. If you are using any kind of power tool or big machinery and you get something stuck in it or have a problem the first thing to do is disconnect the spark plug for a gasoline engine or pull the fuel shutoff if it is a diesel. Then use a stick or other tool to reach in and clear it instead of sticking your hand or foot in. If possible make sure you have someone around to help when you are working on big equipment like farm tractors and make sure that they know how to run and stop the equipment.
Don't trust a jack.When you jack up your vehicle to work under it then put something under it to hold it up in case the jack fails. Jack stands are not very expensive. My dad used sections of railroad tie that he cut off about two feet long. He would stack them up in a pyramid shape. This is good advice even when changing a tire. If you've ever had a truck fall off a jack when the tire is off and had the hub sink so the frame is resting on the ground then you know what I mean.
Don't cut towards yourself.In some situations you have no choice, but as a general rule you want the sharp side of things facing away from you.
When you use a match to look under the seat of an outhouse make sure the match is really out before you throw it in the hole.He made a late night trip to the outhouse one night and the next morning there was just a hole with a bunch of ashes around it.
There are many more but I've got to stop here.