Read the book "Getting to Yes", "a universal guide to the art of negotiating personal and professional disputes". It will repay itself a thousandfold as you walk into any negotiation with confidence, not just salary negotiations.

http://www.amazon.com/Getting-Yes-Negotiating-Agreement-With...

The most underused trick for salary negotiation is actually realizing that salary is negotiable - simply asking one question could increase your salary thousands of dollars.