From twenty years of teaching I'd say that this is the most common gap in understanding amongst guitarists of all levels. Poorly covered, if at all, in all the literature I've read and videos I've watched, it's one of the subjects usually filed in the "keep doing it and you'll get it" section, ie. hit and hope.
Even if you're one of the ones who "got it", defining clearly what we're aiming for in this area can offer great benefits.
In this video I take a look at defining what I'd say are the correct mechanics of chord changes on guitar. This foundational concept is applicable to many other situations, and allows us to approach our problems systematically, letting us monitor results and therefore practice efficiently.