Open Your Hood
Everyday I see drivers do partial vehicle inspections. They walk around their trucks and trailers. Maybe they 
kick the tires. Maybe they don't. They get the flashers going and check the lights. Maybe they check the brake lights. Maybe they don't. More and more of them don't seem to be opening their hoods. Isn't that part of the inspection process? It sure is part of mine.
It could be part of the “car” mentality. The more that these trucks drive like cars, the more drivers treat them like cars. Cars don't get pulled around back at weigh stations. Cars don't come equipped with a 14 hour clock. Car drivers don't have CSA scores. They don't have a PSP. Opening your hood should be part of your inspection routine.
Chances are you are not going to find anything major. You could check your oil. How is your coolant level? Put your hand on your steering rod. How much play is there? Is it the right amount? It takes about a minute to check these items. My truck with 116,000 miles on it has never required me to add oil or coolant. The play in the rod is consistent. Nothing had ever been wrong, yet I check them before every drive, just in case.
Check for the little things. How does your belt look? Does it flex properly? Are your hoses supple? Do you see any fluid where it does not belong. These new DPF engines stay incredibly clean and a leak would be easily spotted. If you have an older engine, clean it. That will make leaks easy to spot. You could have a pin hole leak in a line or a hose. Pin hole leaks have a tendency to not remain pin hole leaks. That minor leak could turn into a major problem. It could eventually cause a breakdown.
What about those hose clamps? Check to see if you can move them. If you can check out why. A simple 
loose or broken hose clamp can lead to a break down. You may end up with a tow job. It could cost you down time. Hose clamps are cheap. Tow trucks aren't. Even if you can't make the repair yourself, catching it before you head out on the road can save you a service call.
Every time I see a truck broken down on the side or a road, I wonder if that driver opened up the hood before they left. Was whatever caused the break down something simple? Could that driver have made an easy repair in the parking lot? Could a simple turn of a screw or a new hose clamp have prevented a break down?