Most people realize the interviewing stage is the last time you'll probably have influence on the amount of your salary. Once hired, your salary is dictated by policy coupled with company and individual performance.
Although this is a common fact, many job seekers lose sight of this during the critical stages of landing the job. They later find out they are paid less than colleagues in similar positions. The key to avoiding this fate is to be armed with information and be able to sell the value you bring.
Do your homework
There are many sources for general salary information on the Internet. Realize that smaller companies typically pay less than the average, but can offer other benefits. It may be tough to find out what current employees earn at a company; however, you might be able to track down a past employee and ask about the salary they were earning when they left. Even if you can find out the salaries of personnel above and below the position you're interviewing for, you at least will have a range.
If you are working through a recruiter, you should share your salary history and then ask to hear the budget their client has set for the position. You should also ask if their client has been known to shift their target salary when the situation dictates it.
Selling your value
Typically, salaries are dictated for the position and its placement on the salary bands dictated by Human Resources at the company. However, where you fall on the salary band may be dictated by what you bring to the table. When interviewing for the job, it is one thing to be the best candidate, and another to be a candidate they can't live without. What is the one skill/ability/technology you know that they don't have? If you have it and they want it, you have negotiation strength. You need to be specific about this and make sure they know about it during the interview stage You can even ask them if members of the current team have this ability. It may very well be something they didn't think to put on the job description.
Your value might also be dictated by your ability to do two jobs at once. If you know they need a marketing manager and graphics person, you might let them know you have done both jobs in a previous role. If you can save them money in the staffing budget, you naturally have the right to ask for more than the position normally earns.
Look for creative compromises
The company may not have the budget or approval for raising the salary to accommodate your wishes. You should be prepared to discuss other benefits that have monetary value to you, but may come from another "accounting bucket" for them. Medical insurance, 401(k) matching, performance bonuses, paid time off, and tuition reimbursement are all benefits that can be discussed. Some companies have flexibility, some don't.
Although the goal is typically to make as much as you can, you must think long term. Getting a good salary at a growing company is better than a more-than-good salary at a stagnant company. At some point, the good salary will likely surpass the other through cost-of-living raises. Plus, your experience and role might propel you towards a promotion faster.
Also, don't expect to make more than your colleagues if you are no better than them. Managers need justification to break from precedence on salaries. Giving you more might require a shift for everyone else (or smaller raises for you while the others catch up). Make sure you are aware of how you stack up to your peers. Their career histories might be on LinkedIn or you might casually ask how long they've worked there and where they were before.
Know when to say when
Managers like hiring candidates who are excited about the opportunity, not overly concerned with compensation. You need to be sure to offset your inquiries about salary with questions centered on how you can make a difference and help the company as quickly as possible.
At the same time, you certainly can say no. If it is not a fair offer, you might have to walk away. This will either lead to the next opportunity for you that may be better, or the hiring manager may reconsider the offer knowing you stand firm on the salary you feel you deserve. Although, only if you truly have the value they seek, will this happen.