This is another of the many manuals by FAO. This one discusses product development, although in a someone theoretical way.
click the image to visit the web page
The manual is broad, covering the following topics:
There is a lot of good information in here although for my liking its a bit theoretical and maybe it could do with some more interesting case studies.
It is, however, worth downloading and reading. It is 35 pages and was published in 2006 so is up to date and comprehensive.