Bobby van der Sluis:

  1. Make sure your JavaScript code is in balance with its environment
  2. Create accessible JavaScript
  3. Create usable JavaScript
  4. Create easy applicable JavaScript
  5. Create future-proof JavaScript
  6. Know JavaScript’s weaknesses, limitations and bugs
  7. Often there is more than one good solution
  8. Write your own scripts or reuse code from trusted places
  9. Optimize your JavaScript code for performance
  10. Use tools to optimize your work process

Full read here: Ten good practices for writing JavaScript in 2005