V. Good UX aims at reducing tooltips, tutorials and FAQs to a minimum.
IV. If your interface makes people feel stupid, they'll try to avoid it in the future. Nobody likes to feel stupid.
III. It's the little things that matter.
II. Never hide primary information behind an additional click the user has to perform! Keep the number of necessary clicks as low as possible. For example, in search engines, do not (never ever!) require a user to click twice before they reach their desired result.