Do you think that car is following your’s? Make four right turn – essentially you are making a circle. If you find that car is still following you after this, drive to the nearest police station or other location with armed security.
If you drive in places where car-jackings are frequent, you might want to consider taking a class in evasive driving techniques. At least remember never to stop in a ‘kill’ zone. Be sure you can always see the tires of the vehicle in front of you when stopping at intersections – so you can go around it if need be.
There are other helpful tips available in books on the topic, but remember is someone is attacking you, you don’t have to be a nice driver.