Top three? 1) Cooling system. NHTSA research shows the single most common automotive breakdown in the US continues to involve cooling system failure. 2) Do good electrical maintenance, something most people completely ignore. It's not called EFI for nothing you know. 3) Inspect and replace consumables (fluids, plugs, wires, belts, hoses, etc) on a proactive basis. Use quality parts. I'll add a fourth. It's simple but lots of people seem to ignore it: Learn. Know wtf you're doing. If you're too lazy to put the effort in don't cry when it comes back to haunt you.
And don't beat on the car too much
Don't assume everything on my car lasted without attention and keep in mind I bought the thing new. I had control over it from day one. Plus the engine was overhauled once during that 22 years. Both of those things can result in longish periods of trouble free service. Add to that I own and maintain aircraft, something that teaches one a great deal about maintaining for reliability. I also live in a mild climate, the car was always garaged, I only drove it locally (160K miles in 22 years) and I had more than enough money to spend on it.
Proactive, not reactive, maintenance is the key along with careful inspections and investing in the tools and knowledge for the job. That means replacing or overhauling stuff before it breaks and any issues that creep up get dealt with immediately. I put my all my cars through a comprehensive inspection and diagnostic process once a year.
I had a few problems but none that stranded me. Some of the success was just luck. Every light bulb in the car except the fogs and heads lasted 22 years. Nobody can figure that one out...
