1. Focus on the Primary Task
  2. Elevate the Content that People Care About
  3. Think Top Down
  4. Give People a Logical Path to Follow
  5. Make Usage Easy and Obvious
  6. Use User-Centric Terminology
  7. Minimize the Effort Required for User Input
  8. Downplay File-Handling Operations
  9. Enable Collaboration and Connectedness
  10. De-emphasize Settings
  11. Brand Appropriately
  12. Make Search Quick and Rewarding
  13. Entice and Inform with a Well-Written Description
  14. Be Succinct
  15. Use UI Elements Consistently
  16. Consider Adding Physicality and Realism
  17. Delight People with Stunning Graphics
  18. Handle Orientation Changes
  19. Make Targets Fingertip-Size
  20. Use Subtle Animation to Communicate
  21. Support Gestures Appropriately
  22. Ask People to Save Only When Necessary
  23. Make Modal Tasks Occasional and Simple
  24. Start Instantly
  25. Always Be Prepared to Stop
  26. Don’t Quit Programmatically
  27. If Necessary, Display a License Agreement or Disclaimer

http://www.significantpixels.com/2012/04/23/apples-27-guidelines-for-mobile-user-experience-design/