A car tune up is generally aimed at cleaning things that are dirty and replacing things that are designed to clog or wear out to return the engine to something approximating its new condition.
Aside from mechanical failure, nothing will slow your engine like worn cylinder walls and weakened piston rings. No amount of maintenance will compensate for cylinders that won't seal combustion gases in to produce power, so do a compression check first before spending money on anything else.
Engine oil and system filters are designed to be periodically replaced. Research your car's maintenance schedule to determine if your mileage warrants changing your air filters, or change them anyway just to be sure.
Drain all of your engine's fluids, run a flushing solution through the system and replace the fluid with something better if possible. Replace your old oil with a high-mileage synthetic that contains seal conditioners that will cause your valve seals to soften and swell, helping to seal internal leaks and reduce oil consumption. Do NOT, under any circumstances, flush transmission fluid with more than 60,000 miles on it. The new fluid won't mix with the old fluid in your clutches, and you'll fry the transmission.
Clean everything you can, including fuel injectors, idle air control valves and channels, throttle bodies, spark plugs (assuming you opt not to replace them) and PCV valves.
