This is a simple process of selecting qualified contractors to generate realistic bids using a thorough set of construction documents. Without the excellent documents, bid management has little meaning. The laborious process of checking qualifications, licensure, insurance and refernces is best carried out by an industry professional, not a homeowner, unless they are eager for the experience.
Once bids are received from the contractors, they must be analyzed for apples-to-apples rationality in order to compare them. This is a very specific proess that is greatly informed by experience in the building delivery process. I have saved clients hundreds of thousands of dollars on a single project by skillful bid management.