Safety first - always wear a seat belt, and urge other passengers to do so. If your car has airbags, they will only work if you are wearing the seat-belt.
Follow speed limits and try to keep in your lane. Use indicators and mirrors while turning. Keep a safe distance from the car in front of you (roughly one car length for every 15 km/h). Never give in to road rage; its not worth it. You will avoid most accidents.
Try to keep up with basic maintenance - check the engine oil level every time you refuel. Pump the tires to at least manufacturer recommendations once a month. At the same time, you may also get the air filter blasted with compressed air (the car wash guys do this for free). Check the battery fluid level and coolant level once a day.