You ll have gained little by negotiating a good deal if you alienate your future boss in the process. The one sure way to lose everything you ve obtained is to be greedy. There comes a point in every negotiation when you ve achieved everything you could have reasonably expected to gain. While most companies will want to treat you fairly and make you happy, few companies want a to hire a greedy hanger on. This may even cause the offer to fall through, or mar your image.
Employment is an ongoing relationship.
Job negotiations are the starting point for your career with a company. Getting something in writing provides closure and prevents any misunderstandings between you and an employer. Take charge of this process by writing a letter spelling out the details of the deal you've agreed to while they're fresh in your mind after the interview. It prevents misunderstandings that might result from poor memories, changed circumstances or, at times, bad faith on the part of an employer.