Before taking any measures I'd recommend to find a reason why it had appeared. There can be a lot of reasons and here are the most popular ones:

Hard water

If you have a hard water running in your tap, you better install filter for its distillation and softening. Or you can buy a bottle water in supermarket and wash your hair with it.

"Wrong" cosmetics

If you, for example, use shampoo for greasy hair while your hair type is dry, it may cause dandruff. Be more careful when choosing your hair cosmetics and don't wash your hair too often.

Zinc Deficit

You have to reconsider your diet so that there were enough of products rich in zinc and replace your shampoo by zinc rich shampoo.

Hormone change

If you have eliminated everything that may cause dandruff and it doesn't disappear, visit dermatologist or trichologist. The reason causing dandruff can be in dermatosis or hormone changes.
Of course, stress may also emphasize dandruff