We all probably do things at different times that are unsafe practices in the garage. I would like to start this thread by listing a few safe practices and let others add to it.
1- Wear safety glasses. This is the most stressed and most overlooked. One small wire off of a wire wheel or one piece of rust from laying underneath the car or flipped off of a grinder can screw up the whole day.
2- Keep a mirror handy because you overlooked #1. If you have to go from the garage to the house you will blink many times before you find the bathroom mirror. I have a rearview mirror mounted to the wall just for this purpose.
3- Keep some hand cleaner in the garage just for the fact you may have to stick your finger in your eye. See 1 & 2.
4- Keep a fire extiguisher in the garage. They are cheap, you can pick them up at WallyWorld and for a few bucks it can save you many thousands.
5- Store chemicals away from any flame. Vapors can ignite. If they do you had better practice #4.
6- Make sure what chemicals are stored together. Different vapors can react with surprising results resulting in an explosion / fire.
7- Keep some band-aids in the toolbox along with some type of antibiotic (Neosporin, Bactine, etc) Better yet, small cheap medicine cabinets are abundent at the local hardware store. I haven't done this yet but is on a list of to-do's.
8- If working around fuel lines / gas tank, never have a trouble light in the same location. Many a garage has burnt down by the bulb busting in the trouble light and gas fumes. Personally I am not a big advocate of incadescent trouble lights anyhow. Also if you use the 500w quartz halogen worklights never have them around where any water / spray can hit the glass lens. The cool spray with the hot lens can cause it to explode.
9- Take a few minutes to wipe your tools down and put them back where they belong. A clean garage is a safer area to work and it will also save one or two days of cleaning it up every so often. Most people find it a struggle to put it back but find it a joy to drag it out.
10- If you are at a buddies garage and he does not practice any of the above...if you hear the words Uh Oh....run like he!!