Check the air filter. Replace if dirty.

There is an idle adjustment screw on the throttle body. Stand on the passenger side, look for a thin vacuum hose on the top of the throttle body coming toward you, the idle screw is brass and just to the left of where the vacuum hose attaches. (I think, I read somewhere that the idle speed should be 780 once warmed up.)

If the idle is constantly bouncing between 500 and 250, your Idle Air Control valve is probably gunked up with carbon. Use throttle cleaner to clean it. (one post I read said remove Idle Air Control valve from the car, pour throttle cleaner in each hole, and soak it for a few days. Cover the holes with your thumbs, shake it a while, pour out the dirty cleaner, repeat until no more carbon shows up in the cleaner.)

Look for vacuum leaks.

I'm currently having an intermittent stalling problem once the car gets to 1/3 normal operating temp until it has fully warmed up. (Adjusting idle higher fixed most of it. I'm probably going to remove the idle screw and clean it this weekend. More than likely there's carbon build up on it. It's a little tricky on my car because the idle screw is sticking/hard to turn and a previous owner did a major job on the slot in the idle screw; almost no grip for the screwdriver blade.)

take care,
ChrisS