Is well maintained. There is no substitute, and no amount of upgrades or modifications which will make up for poor maintenance. Be aggressive with preventative maintenance.
Is equipped with high quality tires. Tires connect your vehicle to the road. They are a critical safety device. Durable ones ideal for your typical weather and road conditions will be more reliable in an emergency.
Is refueled regularly. A half-full tank is the new empty. Ideally, your vehicle never gets below 3/4 of a tank.
Is Rain-X treated during rainy times of year.
Is regularly checked to ensure spare tire integrity. A good tire shop can verify your spare is reliable and make recommendations on tools best suited for changing a tire in the field.
Carries an emergency kit for injuries and illnesses.