Salary Negotiations
Once you know what you should be earning, how do you go about getting it? Start by being very patient. When interviewing for a new position, do your best not to bring up compensation until the employer makes you an offer. If you're asked what your salary requirements are, say that they are open based upon the position and the overall compensation package. Or tell the employer you'd like to know more about the responsibilities and the challenges of the job prior to discussing salary.
Another option is to give the employer a salary range based upon the salary research you've done up front. Once you've received the offer you don't need to accept (or reject) it right away. A simple "I need to think it over" can get you an increase in the original offer.
And if you're ambivalent about the position a "no" can bring you a better offer too. I turned down a position I knew I didn't want, regardless of salary, and received three follow-up phone calls upping the compensation package. Be careful though, if you do definitely need that new job there's a risk that the employer may accept your declining the position and move on to the next candidate.
Here's more infomation on how to evaluate a job offer.
Negotiating a Raise
If you are currently employed and want a raise, start by being prepared. Gather your salary survey information, recent performance appraisals that document the job you're doing, and any other relevant information. Be aware of company policy regarding compensation. Some employers are limited by budget constraints and can only give raises at certain times of the year, regardless of the circumstances.
Have a clear idea of what you want. Determine the salary range you're looking for and justification for the increase and have both ready to review with your supervisor. Be flexible. Would you consider an extra couple of weeks vacation instead of a raise? I know someone who has regularly taken time-off instead of money and now has six vacation weeks a year... Then, ask your supervisor for a meeting to discuss salary. Present your request, supported by documentation, calmly and rationally. Don't ask for an immediate answer. Your boss is mostly likely going to have to discuss it with Human Resources and/or other company managers.