When you say dandruff, there are many things to consider. The first level is simply scaling. This is natural skin shedding. There is no significant itching. The degree of scaling varies from person to person. The skin flakes are mostly white/dry.
Then there is Pityriasis Capitis. Here the flakes are still relatively dry and small but are generally noticeable. There may be some itching but there will not be any pain/pus.
Next is Seborrheic Dermatitis. This is generally associated with hairfall as the fungus enters hair roots. There would be yellowish/greasy flakes, oily scalp, few or many painful/pus discharging hair roots. The flakes are larger and more sticky. The head may be smelly.
Simple dandruff is best managed at home. Apply hair oil sometime before bath, wash with regular shampoo 2 - 3 times a week.
The 2nd stage would require more frequent shampooing using anti-dandruff shampoos available at super markets. Sometimes if the symptoms bother you or you see much hair loss, it may be better to consult a Dermatologist.
Seborrheic Dermatitis almost always requires a consultation with Dermatologist for proper management.
a very good & detailed post!
another thing that i would like to add to this, not directly related to dandruff though, is about the issue of occurrence of boils on the scalp. when these dry up, they leave behind some rough, flaky skin. however, in my opinion, these can be countered through some simple changes to lifestyle, like diet-changes, inclusion of rigorous physical exercises in the daily routine, keeping one's hair relatively short, not oiling much, etc. seeking the root-cause and rectifying it would go a long way in such a condition. as for dandruff, with consistent care, it fades away after a few months/years. teenage-years are what i feel the most susceptible to this, coupled with acne on the face, shoulders, (upper) back (dandruff could also cause small pimples to grow on the forehead).