What's the likely cause of a rough idle?

The car is a '06 Dodge Stratus at ~67k miles and has a rough idle when stopped in drive. Tachometer is steady just a lot of extra vibration that stops at anything above an idle or if I put the car into neutral. Does anyone have any ideas what might be the cause or if there's anything I can do to fix it at home or if I would have to take it to a shop for other tests or to be fixed.