Make sure your vehicle is prepared for driving before you're half way to your destination and need a service call.
Broken belts are one of the biggest reasons for cars breaking down. Belts are easy to locate and replace near your home. Twist the belts. If any are cracked, worn, or delaminating, they should be replaced.
Small leaks can turn into flowing rivers if you drive for an extended period of time. Some of the most common sources for leaks are the radiator, power steering & radiator hoses, or transmission oil pan & hoses. Determine the color of the fluid, and trace it back to the source.
With the engine off, check brake fluid, coolant, power steering fluid, engine oil, and windshield washer fluid. Refill these, and if you are unsure of what to refill some fluids with, refer to your manual.
Check Tire Pressure
Low tire pressure causes you to get a worse MPG, will make your tires run hotter, and make the treads wear down faster; thus they are more prone to blowing out when driving long distances. Make sure they are the correct pressure (as labeled on the tire).