Why I Do Not Negotiate My Salary
I believe an employee's salary is a direct manifestation of the value that he/she brings to the table, as determined by the company itself. Bargaining back and forth does not change that reality one bit.
I think it does make sense to negotiate your initial salary when you first get a job offer. At the moment a company considers hiring you, they have no direct means of evaluating your actual capabilities other than guessing, based on e.g. your résumé and your performance during interviews.
They'll then offer a compensation that is consistent with what they think you can accomplish once on the job (but also depend on their internal salary rates, and perhaps a series of other factors specific to the company). If you think the pay is not good enough, you can either decline the offer, or try to provide additional information to make the case about your (still unproven) capabilities.
If you utlimately join the company, they can always adjust that inital "guess" at your first performance evaluation (say) six or twelve months down the line. So even if the compensation was initially "off", it won't be so for very long.
But once you're on the job and your salary has been determined as a result of your last performance evaluation (or lack thereof), there is no point in bargaining your salary. As I mentioned at the beginning, your salary is what the company thinks you are worth, from the point of view of their business, i.e. their bottom line. Nobody but the company is entitled to make that determination. They are the part that benefits from your labour; they set the price tag.
You may disagree whether it is fair to you, but ultimately it's the company that decides how much they are willing to pay for your value. If you disagree, you need to find another company whose valuation of your work is more in line with your own.
Alternatively, you may agree with how much they value your work, but you may think that you are under-utilized/over-qualified. In such case, I think it is best to first seek a promotion to a job with responsabilities and compensation consistent with what you think you can give. If no such positions are available within the organization, and you still want to do more, then you should perhaps search for such a job somewhere else.
In either case, it is the company's responsibility to conduct periodical performance evaluations and adjust employee compensation accordingly. When the company fails to evaluate its employees, negotiating is not an option.
Some people, faced with the above conundrum, may interview at other companies in the hopes of getting alternative job offers that they can then use as leverage to bargain for a raise.
My blunt opinion here is that, a company that doesn't make a move until provoked this way is low-balling its employees, and offers little hope of career growth.
