The workshop that I run on this subject consists of a number of spreadsheets listing essential items for consideration. I hand them out to participants one page at a time, and then explain how to use them and answer their questions.
I have made them available to readers of this page as PDF files. You will need Adobe Acrobat Reader, freely available from www.adobe.com and other places. Download them, see if they make sense to you as they are - if you have any queries, contact me and I will try to clarify!
The introduction sets the scene and gives some written notes not suitable for the form layout. The forms document gives you some sheets which you can copy and fill in as appropriate.