Hi Justin,
I'd like to add to all of the above a couple more things to consider. Engine tune and battery grounds. A well tuned small block Ford has a strong idle a 650rpm with a stock cam, might need 800-850 with a cam upgrade. Handling a normal headlight or fan load shouldn't stall the motor, although I've been there.
So have look at your spark plugs, if there black and sooty or almost white there carburetor or ignition issues to solve first. Pop in a new set of plugs if yours are not in great shape. Timing or ignition system parts are suspect here.
The alternator most likely has an internal regulator the will not start charging the battery until a minimum rpm has been met, depending on the pulley ratios probably in the 1000-2000 rpm range. So the battery is getting no help at idle if the voltage regulator hasn't joined the party.
The best battery ground is directly to the engine block along with the usual chassis ground. Both have to in good condition, check for corrosion, frayed wires and loose connections. The 12v power output lead from the alternator also has to be in good shape and adequate gauge for its' length.
In the old days (pre EFI) carbureted engines had idle up solenoids to help maintain the normal idle speed (and charging) at high pumping or electrical loads such as A/C, lights and fans.
That said, turning on the a/c, headlights and fans usually will pull the idle not more than 100 rpm if all else is in good shape. A higher base RPM target may be required...
To add to Randys' tell us more about your car, what's changed since the last time it idled well?
Cheers
Ian