These are all great answers, and get to the heart of the matter: you must demonstrate and explain, and provide individual help as needed.
I don’t think there is one best way, as different people will learn differently. Part of what makes a seasoned instructor is the ability to be doing them all, seamlessly, and as needed in response to what he or she sees going on in the class. It is silly to cue ‘drop shoulders’ if everyone’s shoulders are dropped, and good to cue ‘exhale’ if everyone is straining against a weight.
Do be particularly aware if you have older students: their hearing is not always great, especially if a fan and the music are both going. Also their eyesight is not always perfect. And of course, for those who did not do this sort of thing when younger the neuromuscular pathways are not highly engrained. I often will move toward an area of the room and demonstrate closer to someone who seems to need it.
It is also important to use skill in communicating. Some people are touchy that they might be doing something wrong…. If I know someone is like that I demonstrate and talk about form while looking elsewhere, and then nod and smile at them if I see them get it.
In other words, remember that cuing is to a large extent about good communication, and half of communication is listening.