What's the best/fastest way to get rid of dandruff?

Every year at the end of winter, I get a pretty bad danfruff problem. My scalp gets really dry and itchy and I’m a brunette so it’s embarassing and I worry about it constantly.

So what can I buy that isn’t ridiculously expensive but will work? I’ve tried deep conditioning and it hasn’t helped. Does Head & Shoulders really work or should I get something stronger?