What makes an effective mathematics lesson?

Preparatory questions and links:

Focusing questions:
Is effectiveness immediately measurable or noticeable?
What do you see as the criteria for judging effectiveness?
Can a lesson be effective only for the teacher or only for the learners or does it have to be effective for both?
Is effectiveness in a mathematics lesson the same as effectiveness in other lessons?
Is there a difference between short-term effect and long-term effect? If so, what is it and how do you achieve a balance?

(Provided by @ColinTGraham)

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Threaded discussion from Friday 10th December 2010 -
Threaded discussion from Monday 13th December 2010 -

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