If you really want the job, but just don’t feel the offer is what you’re worth (realistically), make sure you negotiate carefully. You don’t want to close any doors by reacting poorly. A written proposal may be the best alternative, since you will have time to polish it and avoid emotional responses that may occur if you are unprepared. In other words, with documentation there are fewer chances to make serious mistakes.
If you decide to attempt negotiations, present any higher offers you have received from other companies. Just saying you have received a better offer from another source will not be persuasive. Ask the company making the more attractive offer to put it in writing. You can later present it to the preferred firm, but do so cordially. A confrontational attitude will not get you very far.
Perhaps you believe that your skills and credentials should garner a higher salary or better benefits as compared to others competing for the position. Be sure to document the details of exceptional skills, important or unusual credentials, volunteer experience in the field, or any awards or commendations you may have received.
When you have developed enough information and organized it in a way that is sure to impress the prospective employer, present your “counter proposal.” Be aware that the employer may not accept your counter proposal, and think about how you will react if that is the case.
Weigh your other options, but also remember to not only present your proposal in a professional, respectful manner, but to accept the employer’s answer graciously as well. This way, the original offer is more likely to still be available if you decide you should accept it after all. Even if you don’t accept it, there is a possibility that the firm could call on you at a later date, so don’t burn bridges.