I'm not a businesswoman, I'm a business, man!
我不是一个女商人,我就是生意,伙计!#
There is no method but to be very intelligent.
The best time to negotiate your salary for a new job is the moment AFTER they say they want you, and not before. Then it becomes a game of chicken for each side to name an amount first, but it is to your advantage to get them to give a number before you do.