Pull straight back. Try to support as much of the rear of the knob as possible with your fingers or a tool that will do the same. Don't put too much 'squeeze' pressure on the knob; they are old, and in a Desert car (mine lived in Nevada most of its life) can get brittle enough that the squeeze will crack them. Also can be helpful if the knobs are warm (sunny day warm, NOT hot).
Some knobs have a metal flat spring in them to provide grip against the switch shaft; cars from humid climates might have rust in there that makes removal very difficult without causing damage. Unfortunately the two penetrants I tried on switches in swap meet instrument panels that had the rust problem (bought here in Ill Annoy) caused discoloration of the knobs (that was WD40 and Kroil).
