"Professional with a very high level of integrity, which unfortunately is quite rare among recruiters." Senior Project Manager Consultant, KPMG
Firms typically determine an appropriate salary range for an open position, and then take into account salary history and expectations when generating a compensation package that is realistic and attractive to candidates.
Negotitations are always on a case by case basis, though these links may be helpful in providing an initial guideline.
Courtesy of The Riley Guide, a directory of employment and career information sources and services.