To get past 200K miles, normal maintenance should do. I waited until 150K to do plugs and wires, mostly because it never had a hiccup. At that time I put plugs, wires, coolant flush, hoses, and thermostat on. At 175 it got new rotors and pads and a thorough brake fluid flush. Its had 50K mile trans svcs. The last svc at 175 included a shift kit, and it eliminated the hard shifts, but I still think a tranny rebuild is going to happen before 250K, even if it doesn't fail before then.
The single biggest thing you can do for the car? Don't ever let it overheat. Watch the coolant tank like a hawk. If you're adding coolant at every oil change, there is a problem.
Next, fix stuff before it breaks. Advantage: You can shop for parts dirt cheap and install at your convenience. Plus, the car is more enjoyable to drive when everything works as intended.