A roadside breakdown never fits into your plans. There are steps you can take to ensure the safety of your vehicle until you get it repaired.
Safety is easiest to achieve if you are prepared before an emergency occurs. Keep a safety kit in your car. At a bare minimum, it should contain flares or breakdown markers of some kind, along with information on emergency tow services in your area. A fully charged cellphone is also a must. If you don't normally use a cellphone, you can keep one in your car — it can still make calls to 911 even if it isn't on a carrier.
More preparation is necessary if breakdowns are a possibility in rural areas or in bad weather. A few blankets, along with some granola bars and water, can ensure both comfort and survival while awaiting an emergency tow truck. It's also a good idea to keep a small first aid kit on hand.
Do your best to get the car as far onto the shoulder as possible. The further you are from the flow of traffic, the lower likelihood of another car hitting yours. Ideally, you will be able to take the nearest exit and fully exit the roadway.
If the battery is still operating, turn on your hazard lights to help alert other drivers to your location. Get out of the vehicle only if safety dictates, otherwise it is better to stay inside with your seat belt secured. For example, if you need to set up roadside cones or flares behind the vehicle, do so quickly, and then return to the car. If you must leave the vehicle, such as to wait in a nearby business, lock it securely, and do not leave any valuables in it.
You may be able to request a certain type of truck to tow your car. A flatbed truck is the most ideal option if you want to avoid further damage to your vehicle. All four wheels will be placed on the flatbed, so the car won't suffer any road damage during the tow. If damage has affected the axles, tires, or frames, a flatbed may also be the only viable choice.
The next best option is the wheel lift truck. The front or rear wheels are placed in a special cradle, which is then lifted so only two wheels of your vehicle remain on the ground. The car is well supported so that further damage shouldn't occur. Avoid hook and chain trucks, though. These also only lift one end of the car, using a hook, but they can cause damage. Hook and chain trucks are usually reserved for use on totaled or junked cars, not those you wish to repair.
Contact a local towing service for more information about emergency towing.