The image shows proscenium staging but it is relevant to any kind of staging because at any point there’ll always be a stage picture being presented. Note that the right and left are those of the actor and not the audience. If an actor stands on a platform or raised area, this is an example of using levels. A character who’s on a higher level than the others in a scene is usually the more dominant one.
People often make the mistake of fully facing the actor they’re talking to. This means that they block out the audience due to the angle at which they’re standing. Even though it probably feels unnatural, it’ll look fine if you both turn towards each other but remain open to the audience. The idea of remaining open to the audience is key to using any kind of stage and to good blocking on the part of the director.
It’s important to think about the ‘pictures’ being created at all times, whether you're working with crowds or with only one performer. If there are a crowd of people listening to an argument they may well need to look as though they are focused on the argument. But they should spread out across the acting space and be angled in such a way in relation to the audience that we can see their faces and reactions. This is reminiscent of the advice you’ll have had or read in relation to creating tableaux or freeze frames.
It’s not just important when you’re standing still, though. Your movements have to be confident to convince the audience. Remember that a timid gesture should be acted by a confident actor. A timid actor will simply make the audience feel uncomfortable. Actions and reactions need to be fully drawn for the audience to understand and appreciate every level of the performance.