Before setting out on a long road trip with your car you should check the car over to be sure it's in good shape to make the trip.
It's no fun breaking down so if something needs fixed before the long road trip you should make sure you get it fixed before setting out on the road trip.
Also it's a good idea to have towing insurance or have the extra money to tow the vehicle if you do have a breakdown.
Things you should check on your car before a long road trip are things such as belts, hoses, engine oil, transmission fluid, brake pads, brake shoes, brake rotors, brake drums, brake fluid, engine coolant etc
Check the tires as well and be sure the tires are properly inflated and make sure the tires don't have cracks or bulges in them and if they do you should replace them.
Also carry extra engine oil with you as well as engine coolant in case you need to add more engine oil and engine coolant.