Start by separating the bent rims from the warped ones. Most are warped, and can be aligned pretty damm close via the spokes. The key is to work by degrees and gently the rim home, not try to force it home by being ham fisted.

Bent ones are for the ham fisted. Brute force working against a fulcrum of some kind can get the rim close enough that the spokes can bring it home. Different bends need different treatments. A radial bend such as you might get from a deep pothole can be addressed by loosening the spokes in the area, and maybe even removing the nipples completely right at the bend, then pushing the bend out with your foot while holding the wheel. Sideways bends (Taco) need to be bent sideways. Usually I pass on these, but once on a tour someone dropped his rear wheel into a sewer and fell over folding the wheel. I removed some spokes where I needed to work, and used the same sewer grate to bend the wheel flat, relaced and aligned. That wheel finished the trip.

There's no single answer, but experienced mechanics in poorer areas or in the third world work miracles saving wheels that the average LBS mechanic here would give up as dead.