Your car should receive a tune-up (often referred to as a "major service") every two years or 30,000 miles, whichever comes first. During this tune-up your car will receive some new parts that will hopefully keep it out of the shop for a while. Here's what needs to be done.

Instructions:

1. Replace the fuel filter.
2. Change the spark plugs (unless they're platinum, in which case you have 30,000 more miles to go). Also examine the spark plug wires and replace as needed. A new set of high-quality wires is worth the cost. They may be permanently attached to the distributor cap, so it will have to be changed as well.
3. Replace the distributor cap and rotor if your car has them (some newer models with distributorless ignition don't).
4. Change the points and condenser if you have an older car (roughly 1978 or older) that doesn't feature electronic ignition. You'll actually want your points changed, or at least adjusted, every six months or so (if they're changed, check the ignition timing as well).
5. Check the ignition timing and adjust as needed (rare for a car with electronic ignition--post-1980--and some cars don't allow this at all).
6. Adjust the valves as needed (unless your car has hydraulic valves). Be sure to replace the valve-cover gasket as well, especially if you see oil on top of your engine.
7. Check the belts. Replace if worn.
8. Check the fluids under the hood and replenish as necessary. Change the oil and oil filter if it's been 3,000 miles since the last oil change.
9. Replace the air filter, which should be changed between major services--every 15,000 miles--as well.
10. Adjust the clutch, if you have a manual transmission (although some cars now sport self-adjusting clutches).
11. Service the battery, cleaning terminals and cable ends.
12. Replace the PCV (positive crankcase ventilation) valve. It can make your car run rough or stall if it gets clogged, and it's cheap and easy to replace.

As with all preventive maintenance performed on an automobile, tune-ups can prevent myriad problems from occurring on a vehicle. The filters replaced can clog with use and prevent flow, starving the engine of fuel or air. Spark plugs have a recommended service lifetime of either 30,000 miles or, in the case of platinum or iridium plugs, 60,000 to 100,000 miles (96,000 to 160,000 km), and old spark plugs may cause engine misfire.