Establish a basic roadside kit. This might include a spare cell phone, CB radio or other communication device. An intact spare tire is necessary for all circumstances. Keep some minor maintenance tools on hand, like a jack, lug wrench and jumper cables. A gallon of water in the drunk can come in handy for radiator problems, squirters or plain, old drinking water in emergencies. A fix-all utility knife, like a Leatherman, is a nice gadget to have.
Stock your first-aid kit appropriately. Obviously, keep minor medications and health items in there, like pain relievers, disinfectants, bandage material, etc. But keep things like thermal blankets, scissors, insect- and bite-treatment solutions and a whistle. It's a good idea to invest in a small first-aid guide that offers basic instructional steps for minor medical procedures.
Invest in extreme acts of nature kits. This includes earthquake and snow-country materials. Flashlights, blankets, water supply, rain gear, matches/lighter and tire chains can be lifesavers given some pretty bad circumstances.