The most important thing we need to say up front: Devote your full time and attention to driving!
Resist distraction. If you feel yourself getting tired, pull over and take a break (at a safe location where there are other people and light).
Develop the habit of scanning for situational awareness. Use your mirrors frequently to check behind and to your sides. Look ahead, as far down the road as possible, to anticipate slow-downs, stops, snarls, crashes, emergencies, or other events which will affect traffic flow. Avoid the "tunnel vision" which often occurs during monotonous highway driving as you focus only immediately ahead or where your headlights reach.
If you experience a breakdown, pull as far onto the shoulder as possible and turn your emergency flashers on. If you have a cellular phone, summon assistance from a reputable source or call for law enforcement response. Otherwise, raise your hood or tie a streamer to your antenna, and await assistance inside your locked vehicle.
If a stranger stops, speak to them through a partially rolled-down window, and ask them to go to a phone and call police or a tow service; do not exit your vehicle until a law enforcement officer or tow operator are on scene. On longer trips, be sure you have water, food, and blankets in the vehicle.
Should you observe anyone pulled off the roadway and apparently stranded or in need of assistance, extend them the courtesy of reporting your observation to the police at your earliest opportunity.
NEVER pick up hitchhikers (your parents were right!)
If involved in a property-damage collision in an unfamiliar or potentially unsafe location, do not open or exit your vehicle. If you have a cellular telephone, summon law enforcement. If not, acknowledge the accident by hand signal, and motion the other driver to proceed with you to a safe location (where there are other people and light) to exchange information. If unable to proceed, honk the horn to attract attention and ask a passer-by to summon police.
Criminals sometimes deliberately cause minor car crashes in order to rob the occupants or steal the vehicle (so-called "bump-and-rob" or carjacking). If you are involved in a collision which seems suspicious, remain in your vehicle. Get as far off the roadway as possible, and turn on your emergency flashers. Do NOT get out to inspect for damage or to exchange information.
Summon a law enforcement officer or signal the other driver to follow you to a location where you can safely do so. If necessary, sound the horn to attract attention and await help while secure in your vehicle.
If the driver of another vehicle tries to force you off the road, do not stop. Slow to a safe speed, and proceed to a safe location. Try to obtain the license plate number and a description of the other vehicle and its driver and any occupants. Report the occurrence to the police at your earliest opportunity.
Keep your car in gear while stopped at traffic signals or signs. If approached in a threatening manner, honk the horn to attract attention and drive away (as you can do so safely).
Consider car-pooling or ride sharing only IF you have a dependable means of assuring that the other participants are legitimate and safe. Some jurisdictions maintain a central coordinating office for such services; check your telephone directory or on-line. Ride sharing for long trips is NOT recommended unless you are personally acquainted with the other party and fully trust them and have confidence in their driving ability and common sense. Remember; you life is literally in their hands while they're behind the wheel.
Before your trip — Consider leaving a copy of your travel itinerary with a trusted family friend or relative (plus a driving route map or flight/bus/train trip info).
If signaled to stop by any vehicle other than a clearly marked law enforcement unit, acknowledge the signal, and wave the driver to follow you to a safe location (where there are other people and light). Drive within the speed limit and take the shortest possible route to the nearest safe place. If you have a cellular phone, dial 9-1-1, tell the call-taker you are being followed by an unmarked vehicle attempting to stop you, and ask them to send a marked law enforcement vehicle to your location.
roll up the windows, lock the vehicle, take the keys, and insure your valuables are concealed (preferably in the trunk). During hours of darkness, park and walk in lighted areas to the extent possible.
While carrying large amounts of cash should be avoided, you should have enough small bills and change to cover on-the-road purchases, including fuel should you run low while in an area where stations don’t accept the cards you carry. Enough for a half-tank fillup, taxi or bus fare, snacks and drinks or a phone call should be sufficient. Traveler’s checks are safer, but are not universally accepted. Keep your wallet, purse, and any other valuables on your person or otherwise out of sight, NOT on the seat next to you.
If you must leave valuable items in your car while out and about, place items out of sight before reaching your destination or move them inconspicuously. This includes packages, backpacks, gym bags, GPS units, MP3 players, and so forth. Someone may be watching when you put items under/behind a seat or throw something over them. An opportunistic thief is on the lookout for "trunk-packing", and can break into your car the minute you're out of sight.
One reason SUVs and pickups are common auto-burglary targets is because they don't have a "trunk" to hold valuables — the driver/passenger generally just "hides" their valuables "out of sight". The thieves know this, and do check glove compartments, behind seats, and under seats. It only takes a few seconds to check all the "usual" hiding places.
Unobtrusively locking everything valuable "in the trunk" (if you have one) may be difficult when you're combining errands at multiple destinations. Certainly avoid leaving packages or shopping bags visible in your car - lock them in the trunk out of sight if you have to leave packages in your car unattended.
Plan your shopping/errands so that you don't load your trunk until you are ready to drive to another destination. Load your trunk when you leave a location — never open a trunk, fill it full of valuables, close it, and then just walk away to do more shopping or other errands.
Source of information, courtesy of the University of Oklahoma Police Department, http://www.ou.edu/oupd