Be clear, in your own mind, about exactly what you're after.

Do your homework, so that you are fully prepared to discuss every aspect and respond to every question and comment.

Be persistent. Don't expect to "win" the first time. Your first job is just to start the other person thinking.

Make friends with the person with whom you are bargaining. Put your bargain in terms of his or her needs, advantages, and benefits.

Keep your sense of humor.