This subject is more related to development approaches (such as software development or engineering development) than pure project management, but is essential to good project delivery. A few specific references are:
The Definitive Guide to Project Management (Financial Times Prentice Hall) by Sebastian Nokes et al., 2003, Chapters 10 11.
The Project Workout (Financial Times Prentice Hall) by Robert Buttrick, 2nd edn, 2003, Chapters 8 11, 27.
To Do Now
Review your Project Plan. Ask yourself, is there anything else you need to do to make sure your customer will really benefit from the results of the project?
Make sure you have built all these tasks into the Project Plan and Project Budget, and that you have people in the project team allocated to these tasks.