After you have your minimum requirements in place and you have come to the negotiating table, be firm. Although you must be creative and flexible, you must also have a point at which you do not give in.
This can be difficult in the face of a difficult job market or a long and drawn-out job search. But a minimum requirement is not a desired salary. Your minimums should be based squarely in the reality of your current job situation and primary financial needs.
I am assuming that you have not oversold your qualifications and that you have a realistic idea of your worth to the company. Also, if you have been building your network of contacts and getting your name to numerous companies, you will likely have more opportunities in the wings. More opportunity also produces more confidence in the negotiation process.