See if The Potential Job Meets Your Career Goals
This is the point where you focus on the job itself. There is no use in negotiating for a better package for a job that will sap the life out of you or derail your career. Figure out if you want the job itself, do you know what your prospective employers expect from you? Is it something you can deliver on? By finding out the answers to these questions you can know whether or not you should push for a better compensation.
Find Out All The Particulars
Examine the offer you have been given. Look at the various clauses and get an idea of what your prospective employer is trying to sell to you. If you need further explanation, do not be afraid to ask. Find out about how bonuses and other perks are structured, how much you will be paying in income tax, any monthly deductibles that will affect your salary and more importantly find out how much you can call your take home pay. Do not let a bunch of big figures on a piece of paper blind you.
Know Your Minimum and Target Salary
A minimum salary is the lowest figure you would be looking to accept. The target salary is what you would ideally accept. You can disclose your target salary if you wish to but the minimum is your secret. Without figuring this out, you cannot adequately know whether or not a job offer is right for you.
Even if you are going to reject the offer be polite about it. Antagonize your prospective employer and you might as well negotiate against a brick wall. Acknowledge the offer, do not delve into specifics. Just let them know you like the offer of employment, just not these terms you are currently looking at.
Find out what the average pay is for a professional in your capacity. This requires some espionage on your part. Use this opportunity to figure out the expected job descriptions you will be required to fulfill, this can be used as leverage later on.
Negotiate from a Good Position
By knowing what your future employer needs from you, you can know how much negotiation room you have. If you are coming in to setup a new unit, revitalize a struggling department or meet a specific skill gap then you can go all the way but if you are looking to get your foot into a certain industry with a limited set of basic skills or experience, you should probably know that you have little room to maneuver.
Ask for More
During negotiations, never throw out a number but state your opinion about the low offer you have in your hands. By doing this you force the employer to offer you a number. If you did blurt out a number, the employer might be tempted to add to your main salary. After tax considerations, you might not see the full value of the increment.
Present A Better Offer
As a last resort, present a better offer to your prospective employer. When you do this you can discuss salary but work your pitch more towards perks and side benefits. You might be looking for a higher contribution to your pension plan, a bigger medical/dental plan to include your loved ones or an extra allowance of some kind.
Get Everything In Writing
Put everything in writing, even the items that are conditional i.e. those based on performance. Make sure it is legal and can be used to hold your employer accountable.
Never Burn Bridges
Even when you cannot agree on a job offer, do not leave the discussion with hurt feelings. It is simply business, when you go to a store and cannot afford an item you do not take your emotions out on the salesperson. So it is in this scenario. Be thankful that you where considered for the role and end the conclusion in a way that would remind your prospective employers why they should have hired you rather than being grateful that they dodged a bullet.