"I'm not paid what I'm worth." Who hasn't said this at least once? I certainly have. But if we subscribe to classical economics which says that the price paid for any given service is the price at which the quantity supplied equals the quantity demanded, aren't we paid precisely what we're worth? And if we still believe we're trading at a discount to our intrinsic value, is it possible to change the market's mind?
Salary surveys, talking to other people in similar positions are reasonable starting points. In my opinion, getting a competitive offer now and again (by interviewing elsewhere) is the easiest way to make sure that you're being adequately compensated.