Idle problems Options

[Coligion]

I've dug through a lot of the past topics on this through the search fuction, but thought I'd better get some others insight. Basically, my idle is just not consistant. When I start the car up cold, the idle will be about 100-200 RPMs too low (the car will shake/vibrate). Usually I'll warm it up by holding the gas down for a bit and usually the RPMs will rise to a mostly steady 800 RPMs. When driving at night my RPMs also suffer from having my low-beams/fog lights on (the idle is already taxed, and having the lights on adds to it). Lastly, having the AC on will greatly affect the RPMs. What usually will happen is that I'll be driving around town at 45 mph and then come to a light with the AC on and the RPMs will fall dramatically (below 500) and my car almost wants to die.....but then a few seconds later the idle will correct itself to somewhere near 800. This is fairly constant though, that is, whenever I come to a stop when having the AC on the idle drops far too low, but then corrects itself. Having said all that, the idle is perfectly fine at normal speeds. The only issue is when the car is stopped. Obviously, this is an annoyance and I would surely like to remedy the problem. Am I looking at replacing a coolant temperature sensor? The AIC? Any help is appreciated.