If a car is sputtering when you try to accelerate, this indicates that it is time for a tune-up. A full tune-up of the engine is in order, rather than only swapping out the spark plugs. Ignition misfire is one of the symptoms that the engine is in need of some help; the sputtering is a sign of bad timing that also causes damage to other engine components.
When performing a tune-up on a car, check the entire secondary ignition system. This includes the ignition coil, rotor, cap, wires and plugs; some mechanics recommend a PCV valve as well.
If the tune-up does not solve the problem, air intake is another (although much less common) possibility. Look at the intake hose for cracks because if the system is not airtight and a car has a mass air flow sensor, sputtering at acceleration is one possible sign. Repair any air leaks that are present and then test the engine again. The reason why air leaks cause sputtering is that the air-to-fuel ratio is hampering the performance of the engine. For the best results, take the car to a shop, and then inform the mechanic all of the steps taken so far.