The problem is that people who know exactly what they want are rare.

Sure, if someone says "I want to learn what are the common ways of setting up lighting for portraits, what they achieve and what their trade-offs are" it's easy to teach him.

But more often people will say: "I want to make better pictures". What do you mean, better? -- "Well, you know, better..." :-)

I think this is one of the cases where asking the right question is much harder than coming up with an answer...

Fey