It's been a while since I looked for a job, but in the past most places have always asked me my salary requirements along with my resume. I always put the minimum I will accept as the bottom of the range. THen, if they offer me that, I just take it. If they offer me less, I just forget about it - I figure they are playing games.
But it's true you can't trust some employers. When I worked in semiconductor capital equpment everybody was a customer or a competitior and they all knew the staff at other companies. My company kept telling everyone they couldn't afford raises. So, one fellow left, and then the company that hired him made offers to about 10 other staff at my company at 10% raises. On hearing this, my company offered 5% on top of that for them to stay. But some people were so annoyed with the shenanigans they left anyway. And my company actually sued the other company for unfair business practices or some such nonsense. It was ridiculous. THey lost obviously.