Agree absolutely with the general principal of what Gus says.
I teach to wait until you think you're going to hit the runway, then shift vision to the end of the runway (or the middle of the runway if we're using the big runway), then judge your height above the runway. If you now appear to be far too high (which you invariably will be), go back to flying the right attitude for a couple more seconds, then repeat. Once you are at the correct height above the runway, raise the nose and flare as Gus described.
The next question is what is the "correct height above the runway". Having a big runway helps here. After landing, take control from the student and use power to maintain speed to slightly below Vr. Get the student to look to the end of the runway and note how the runway looks, paying particular attention to the perspective of the edge of the runway. If there's enough runway remaining, now raise the nose and get the student to observe that although the amount of the runway he can see has changed, the perspective of the runway hasn't. Explain to the student that as he begins to flare and then continues to hold off, the nose will rise, so the amount of runway visible will change, but his aim is to maintain the height above the runway by maintaining the perspective that he's now looking at.
The most important thing, though, is to be positive with (almost) every student on every flight at this stage. Remember when you were learning to land, remember that the highs and lows are natural, and that everyone has to work hard to learn to land consistantly, so even if the student has a bad flight, try to finish the de-brief on a good note. The only exception would be a student who is seriously over-confident.
Haven't heard the runway edge at the shoulders before, at least not for daytime flying, but I can see that it works. At night, I teach to let the edge lights rise to the level of your ears, which I guess is pretty much the same thing.
As Gus said, though, everyone's different, so what works for one student (or one instructor) might not work for the next.
FFF
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