Regarding your last point here about asking for 10% more than what you’d need/your lowest quote would be, I can’t agree more. I think a lot of people will be pleasantly surprised as well that they can get that extra 10% quite easily. People undersell themselves, especially women I feel, all the time.

-do the market research, again, not just via sites like salary.com. talk to people doing what you do or aspire to do, and check with industry associations, which often do salary surveys.

-instead of coming right out and asking another professional their salary or rate (which can come off as rude), ask what salary or fee range they think someone with five (or however many) years experience in the field can command. or call your competitors and pose as a potentially interested customer. or check their site; some professionals will post their rates online.

-before you negotiate, figure out what amount of dinero you need to get for the gig in order for it to be worth your while, of course factoring in what the going rate is for someone with your experience level in that industry and geographic region. if that amount is $50K a year (or $50/hr), tell the hiring manager you want 10% more. that way if they haggle with you, you’re not starting at your “no way i am doing it for less” amount.