Make sure you understand how companies will be graded and what factors will determine the final decision. Make them understand that you can give them what they want at a fair price in a deal that makes them happy. Be ready to accept defeat or prepare your options for fighting the decision. A failed proposal does not condemn a company. Simply move on and find another opportunity.
Agencies have specific guidelines for formulating proposals and bids.
The RFP or IFB will ask for certain qualifications that you must demonstrate in writing. A simple way to approach proposals and bids is to respond to each part of the request, point by point. Show why the agency should trust you rather than somebody else. Tell the truth and state your case as explicitly as possible, describing every necessary facet. This is supposed to be your best offer.