We as women are often peacekeepers and people pleasers at work. It is often difficult for women to step out of the female archetype of "nice" when negotiating for a promotion, salary, or new role. Here are three things to remember.
1) NEVER Take Your First Offer
Once you have gotten to the salary negotiation phase they usually want you on the team. No one is going to let a great player go based upon salary. If they really have no budget perhaps intangibles can be negotiated (higher title, contract writing that a raise of x percent will happen based upon Y performance, etc.).
2) Get EVERYTHING in Writing
Make sure EVERYTHING is in writing. When you have good relationships with co-workers it may seem that you can go off people's word however you never know if people may leave and their promises go with them.
3) DOUBLE your Salary or Raise Request
When you are negotiating a new salary or a raise, your company will likely try to negotiate. To land at the amount you really want always double the number that you would like. If you get the raise, FANTASTIC, you just doubled your expected amount. If not -- they will likely meet you in the middle (the place you really want to be!)