It's based on how you hold the relationship between you and them in your mind. Writers have the same problem, but slower (:>). My father, who did it (writing) for a living, advised someone once that what worked for him was to write as though "composing letters to a favorite aunt".

If you imagine you are being charming to that foxy dewy-eyed lass in the front row center -- or the back of the room, for projection-- it'll go like butter, doncha think?

A