Women often...

• Take the first offer.
• Compromise too easily.
• Feel pressured to work for less money than their male counterparts.
• Provide too much information about themselves which could be used against them in the negotiating process.
• Show emotion during negotiations.
• Avoid confrontation and prefer to agree to everything without a challenge.
• Feel pressure to sacrifice family time for work and thereby fail to negotiate adequate personal, vacation, and sick time.
• Avoid making demands during negotiations.
• Avoid making counter offers.
• Underestimate their “worth” to the employer in terms of salary and performance.

By not negotiating effectively, a woman can leave $500,000 on the table over the course of her career.

A very revealing read about the ways women inadvertently harm themselves in negotiating is Women Don’t Ask: The High Cost of Avoiding Negotiation and Positive Strategies for Change by Linda Babcock and Sara Laschever. The authors don't just document the problem but also provide many practical suggestions for making negotiating easier and more productive.