What do you put in that "Salary Desired" box?

A friend of mine is looking for a new job. She has years of experience in the industry, great technical skills, wonderful contacts, and plenty to brag about. But like most of us, she's stymied when a job ad asks for a cover letter, "complete with salary history and requirements." A recent position opening added, "The salary information is important! If you don't tell us what you want to be paid, we can't tell if we can hire you."

We all know the reasons that employers do this: they want to confirm that your background is somewhere in the right range. And, of course, you know they'll sort the acceptable résumés in order of the cheapest-to-acquire candidates. But it makes the process no less frustrating.

My friend has a nice, vague, generic answer to trot out when companies ask for salary history and requirements (though I'm not sure precisely what it is). But, she complained, "Well, then, gee, say the salary range in the ad. Or just get the resumes, and say, 'You look like a promising candidate, but the job pays $10k a year, are you still interested?'"

Besides: how can someone reasonably say how much they expect to earn based on a three-sentence job description? There's no clue about the nature of the company, the unthankfulness of the job, the joy of the social goals. You can make some guesses about what a job pays, but even salary.com and indeed.com give very rough approximations (and I think indeed.com compiles the data from the positions that do include salary data, which usually are cheapskates who know they'd better warn you). But, as my friend said, "Asking for salary requirements before someone has interviewed is like asking if you'll put out before the date even starts!"

Personally, I've never found a good way to respond to those "salary expectations" requirements. What have you done?