A good Business Case is provocative, politically astute, practical and purposeful. It enables a group of cooperating individuals to initiate an endeavour and to progress it constructively.
People are always searching for a suitable approach. In fact, there are many different ways to go about it. This document is made up of templates that each address a particular angle on the Business Case. You'll only need some of them. And they should help you to improve your checking, thinking, planning and doing.
Here is the document: Build a Business Case Templates
Not all is self-explanatory, and you are welcome to request a version with all explanations:
irstokes @ metanaction . com