Customers want to know how you keep up as well as what you have done. As my number of consulting gigs increased I began to amass quite a collection of programs, diagrams, documents, tools and experience. Reinventing the same stuff is a sin. The independent consultant with any hope of being self-supporting must have an organized library of information available at a moment's notice. As the consulting gigs grow in complexity so must your ability to communicate complex solutions in nontechnical ways.
Every customer likes to know they are getting their money's worth.
Deliver a fair, honest, objective assessment to your customer. We must understand clearly the needs of the customer, the problems they are toiling with and the urgency of their situation. This can be as simple as looking at the code and as complex as documenting and diagramming the customer's entire business process. The final product of an assessment should be impartial in nature and of value to the customer. The successful consultant does not go into an engagement blind.