See Figure 1
Do keep a fire extinguisher and first aid kit within easy reach. Know how to use them before you need them.
Do wear safety glasses or goggles when cutting, drilling, grinding or prying, even if you have 20/20 vision. If you wear glasses for the sake of vision, they should be made of hardened glass that can serve also as safety glasses, or wear safety goggles over your regular glasses.
Do shield your eyes whenever you work around the battery. Batteries contain sulfuric acid. In case of contact with the eyes or skin, flush the area with water or a mixture of water and baking soda and get medical attention immediately.
Do work neatly. A few minutes spent clearing a workbench or setting up a small table for tools is well worth the effort. Make yourself put tools back on the table when not in use; doing so means you won't have to grope around on the floor for that wrench you need right now. Protect your car while working on it with fender covers. If you don't wish to buy a fender cover, an old blanket makes a usable substitute.
Do use safety stands for any undercar service. Jacks are for raising vehicles; safety stands are for making sure the vehicle stays raised until you want it to come down. Whenever the car is raised, block the wheels remaining on the ground and set the parking brake.
Do use adequate ventilation when working with any chemicals or hazardous materials. Like carbon monoxide, the asbestos dust resulting from brake lining wear can be poisonous in sufficient quantities.
Do disconnect the negative battery cable when working on the electrical system. The secondary ignition system can contain up to 40,000 volts.
Do follow manufacturer's directions whenever working with potentially hazardous materials. Both brake fluid and antifreeze are poisonous if taken internally. Housepets and small animals are attracted to the odor and taste of engine coolant (antifreeze). It is a highly poisonous mixture of chemicals; special care must be taken to protect open containers and spillage. If a housepet drinks any amount of coolant, it is a drop everything emergency - seek immediate veterinary care.
Do properly maintain your tools. Loose hammerheads, mushroomed punches and chisels, frayed or poorly grounded electrical cords, excessively worn screwdrivers, spread wrenches (open end), cracked sockets, slipping ratchets, or faulty droplight sockets can cause accidents. Working on your own car is not supposed to be a painful experience.
Do use the proper size and type of tool for the job being done.
Do, when possible, pull on a wrench handle rather than push on it, and adjust your stance to prevent a fall.
Do use socket, open-end or box-end wrenches where possible. They are made to a precise measurement and will fit the hardware exactly. If you must use an adjustable wrench, be sure that the jaws are tightly closed on the nut or bolt and pulled so that the face is on the side of the fixed jaw.
Do select a wrench or socket that fits the nut or bolt. The wrench or socket should sit straight, not cocked.
Do strike squarely with a hammer; avoid glancing blows.
Do set the parking brake and block the drive wheels if the work requires the engine running.
Fig. Fig. 1: Always use jackstands when working under the car