After reading this thread, I got even more interested in typing people on sight. Interested enough to decide to post this topic.
So, start off with primary functions. Once you discover a person's primary and secondary functions, the others fall into place. How do you decide what a person's primary function is? How do you tell the difference between the primary and the secondary, particularly when you are in situations where they are using their secondary function a lot? I know E and I are very simple, but what's the difference between Fi and Fe? etc . . . use lots of examples and anecdotes for us S types.