With a newbie, I start out by talking about how the day will progress. I do this very succinctly. They've paid a lot and want their money's worth. I emphasize the line. After all, without driving the line, you don't know if you're doing better or not. On a newbie with a fast car, I'll have them run in third. Then we'll do a lap sans-brakes to give them a feel. After that we'll move to a specific corner and figure out how to shift and trail brake.
And most of all, I'll look for "the red mist". I'll check my mirrors often, watch the corner workers, and watch the instruments...
On advanced students I emphasis good judgment. For example, knowing not to drive 10/10ths (or 11/10ths) with someone on your back bumper. You owe it to them NOT to spin. I base a lot of my decision to sign them off on what they do when things are out of kilter. Examples are passing off line, Going too deep into a corner, being able to catch a car as it starts to spin…
Mostly, I try to teach them not to run into me when they’re signed off.
