My personal opinion, by no means fixed, is that you get 3 (tightly-related) questions, then after that, it's time to point them to different resources; not that I can't answer more questions, but if it doesn't seem that the asker is learning as opposed to just following ("teaching a man to fish" as opposed to "giving a man a fish"), then answering any more is going to have no effect.

However, others might stop it at fewer questions, others might let it run on longer. But the key thing to note is that when you end such a line of questioning, try to be as friendly as possible and provide as many reasonable resources where the asker should go.

And of course, if after one or two questions, you quick realize it's a homework troll ("My teacher said that we..."), then definitely get out of the line of questioning earlier, but again, try to back out as friendly as possible.

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain