1) Try to get to the hard shoulder or safety zone before the vehicle stops.
2) If you have a flat tyre, consider travelling very slowly to a lay-by or side road if there is no room to stop.
3) Turn on the hazard warning lights - if fitted.
4) Turn off the engine and apply the hand brake and warn other traffic that your vehicle has broken down.
5) Check the local road rules for the acceptable ways to do this. Raising the engine hood is one way.
6) Stay by your vehicle, but get out on the side away from the traffic.
7) Call for help - Call the police or traffic authorities and local autombile breakdown service if you cannot fix the problem yourself.
8) Make sure you have a warning triangle to use in case you break down. Its not always a requirement but definitely always a good idea. Leave it at least 50 meters behind your car if you break down; on freeways about 100 m are better. It will prevent you being rear-ended if you have to stop in an unsafe location.
9) A tow-rope and jumper cables are also handy.