Well the obvious thing is keep it maintained. Oil, all fluids, make sure belts are good. Also do what I did, replace the spark plugs, wires, caps, pretty much cheap repairs/ replacement on things that are older and or bad, it makes a huge difference. You can get rust olum and spray the bottom or I had my done by a rhino liner professional, costed me a good a bit but he did a great job and that was almost 2 years ago. I was down there the other day, and still no rust rust coming through. Pretty much just stick with the obvious fixes/repairs. Keep up on maintenance. I got a 94 jeep about today I'm going to be hitting 180,000 miles and the thing still runs like a charm.