Find your own style. You may find it difficult to strike a balance between being overly passive and too aggressive. Use negotiation as a problem-solving method rather than as a game or adversarial process. Adopt whatever style feels right and natural to you. Consider your needs, your values and the organization that is offering you a job.
Smaller organizations are likely to be more flexible, but pay less.
Larger employers may have more rigid personnel policies but will probably offer a wider range of benefits. It is important to know when to negotiate and when not to. Negotiation can be difficult, particularly if you have never done it before, and it involves some risk. You don't want your prospective employer to have a negative impression of you even before your first day of work. On the other hand, you need to feel confident that this work will not only reward your values and your interests in social change, but will allow you to meet your personal needs.