Around December 2011 the awesome crowd around Heroku released a now open-source document that describes 12 factors that build up a methodology of developing software-as-a-service products.

The main goals of those 12 rules are:

• minimizing effort to board new developers
• maximizing portability
• encouraging continous deployment
• allowing to scale effortless

If you are developing a SaaS product this document will show you lots of ways to improve your development practices. Fortunately it is not directly coupled to any specific language or development environment (most tool examples are coming from Ruby, Python and Clojure though) so that everyone will have something to take away.