Simplicity and Consistency

Simplicity

• Do everything the simplest way imaginable.
• Don't add functionality before it's needed. 
• Refactor code whenever and wherever possible.  (Remove redundancies, clean up ugliness)
• Leave systematic performance optimization until the end-  it may not be needed

Consistency

• Collective code ownership. Any team member can make changes to any piece of code
• Code must be written to agreed stylistic standards.  (Unimportant which standard, just that there is one that everyone uses.)
• Move people around- avoid islands of knowledge. 

Other Aspects

• The customer is always available.
• Choose a system metaphor for the application- gives common ground for technical and business people.  (e.g. application as production line, bill of materials, etc. )
• No overtime work.  (Well, very little of it.)
• A stand-up meeting starts each day.  Many people only need to know result, so shouldn't need to wait long.