I am writing this HOWTO in order to share what I've learned about negotiating salary and benefits, as I realized I was giving the same advice over and over again to my friends and peers. My experience is primarily as a female software engineer in the United States, so your circumstances may vary. If you aren't sure whether my advice applies to your situation, ask other people in your field—preferably well compensated people—for additional advice. (This is good advice in any case.) Finally, this HOWTO is most useful if you read it long before you start job-hunting, as it helps to prepare in advance.
I make a lot of statements in this HOWTO like "Women are paid 75% of what men are paid, on average." These statements are based on my research over about five years on women in computing. For the specific studies behind these statements, and for a wider, more thorough review of women and negotiation, I recommend Ask for It (for practical hands-on advice) and Women Don't Ask (for a more research-oriented survey), both by Linda Babcock and Sara Laschever.
I originally wrote this HOWTO in part because so many of the women I recommended Women Don't Ask to came back and said, "Yes, I want to start negotiating, but do you have any practical advice?" I wanted to fill the gap for them and so wrote this HOWTO. It turns out that that is exactly what happened to the authors of Women Don't Ask too, so they wrote an excellent book on learning practical negotiation skills for women, Ask for It. I highly recommend this book for any woman looking to get more out of life. Go read it - you won't regret it!
I have been on the job market from 1999 through the present - both boom and bust times for my field. I currently get around 2-5 emails per week from recruiters or colleagues asking if I'm interested in a new position. I have received on the order of ten formal job offers, and successfully negotiated about half of those offers (the other half I either turned down or accepted as-is). I have researched salaries for my field and conducted unofficial salary surveys of my own. I am part of an active information sharing (a.k.a., "gossip") circuit of people in my field regarding how we negotiated our compensation. In other words, I'm no expert, but if you're new to negotiating your compensation, the advice in this HOWTO can easily make you thousands of dollars the next time you accept a job or raise time comes around.