How to answer the "What salary are you looking for?" interview question

I think The Onion last year had the best answer to the toughest interview question there is: "My greatest weakness is how I answer this question".

Another tough question is when they ask you what salary you want for the job. This article offers some good advice on how to negotiate salary:

The right answer to the question, “What’s your salary range?” is almost always some version of “I’m not telling you.”

The person who gives the first number sets the starting point. But if that’s you, you lose... The more times you can fend off the question, the less likely you will have to be the one to give the first number...

What did you make at your last job?
“This position is not exactly the same as my last job. So let’s discuss what my responsibilities would be here and then determine a fair salary for this job.” It’s hard to argue with words like “fair” and “responsibilities”—you’re earning respect with this one.

What are you expecting to make in terms of salary?
“I am interested in finding a job that is a good fit for me. I’m sure whatever salary you’re paying is consistent with the rest of the market.” In other words, I respect myself and I want to think I can respect this company.

I need to know what salary you want in order to make you an offer. Can you tell me a range?
“I’d appreciate it if you could make me an offer based on whatever you have budgeted for this position and we can go from there.” This is a pretty direct response, so using words like “appreciate” focuses on drawing out the interviewer’s better qualities instead of her tougher side.

Why don’t you want to give your salary requirements?
“I think you have a good idea of what this position is worth to your company, and that’s important information for me to know.” Enough dancing–this is one last attempt to force you to give the number first. Hold your line here and you win.