For the gear shift and turn signal knobs, use an open end 5/16" wrench and place the wrench behind the end of the knob along the shift or turn signal lever. Smack the side of the wrench a few times and the knobs will start moving off the lever. Once they get so far down you can pull off by hand usually.
For the wiper control knob, there is a set screw on the hub of the knob which can be loosened with a standard small screwdriver.
The Majic-Air knobs also have set screws on the bottom. These are made of pot-metal and can be cleaned up and repainted with black enamel. Replacements are not available.
Headlight switch knob can be removed from the switch by pressing the button on the switch and pull the knob out, but the knob is molded onto the shaft, however, if your knob is in real bad shape, you can swap the knob/shaft with a better one from a donor car.
Left air knob is molded onto the end of the cable.
If knobs are dirty you can try to clean with very mild dishwashing detergent, then polish them with a clean terry cloth to get their shine back.
If they are nicked or faded, I have been successful with rubbing the affected areas with fine steel wool then polishing with fine rubbing compound, then polishing with a terry cloth to get the glossy black shine again.