Check out this article on 8 best dandruff shampoos!

I've always had dandruff.  I got it from my dad, who has it worse than I do.  I don't get it anymore though, only if I don't wash my hair often enough or if I scratch my head too much.  

I would recommend T-Gel from Neutrogena.  It's a strong shampoo which gets rid of dandruff very well.  I would only use this every second or third time you wash your hair, more or less depending on the level of dandruff you experience.  All the hair stylists I've been too have said it's a good thing to use and to use it along with your regular shampoo in between washes, because it is strong, and using it too much could dry out your hair.

 Also, If you have thin hair, I would recommend washing your hair more.  I have thick hair so I wash it every other day, more than that makes my hair unmanageable as it's too clean to hold.  But having dirty hair can make you scratch your scalp, causing your dead skin to be scratched off, becoming flakes of dandruff in your hair.  So make sure you aren't scratching your scalp, or even using rough bristled brushes too much or too close to your scalp, as any contact with your scalp could cause more dandruff.

If these things still don't work, you can see a doctor and he can most likely prescribe something to you or recommend a proper shampoo or treatment (even just vitamins perhaps) to help you.

I hope my post is helpful!

Mix apple cider vinegar to equal parts of water. Pour it over your hair after shampooing/conditioning and let it be(do not rinse). The smell will evaporate as your hair dries.

It will neutralize your hair and scalp - no more dry scalp or dandruff.