It’s important to have realistic expectations before negotiating a salary offer. Employers base salaries on what they currently pay to fill similar roles and what they believe competitors are paying. They may also have a predetermined range or other budget constraints. Find out what people usually make doing the job (including at the hiring organization) by searching websites such as Salary.com, Vault.com, and PayScale.com. And reach out to people in your network who can give you insight — somebody you trust inside the organization, a career adviser, a search consultant, contacts in the same industry. Compare their feedback — don’t rely on one source.
Adapted from the HBR Guide to Getting the Right Job.