Jakob Nielsen created the Ten Usability Hueristics.  Watch this video to gain a quick understanding of what these ten steps are and how you can begin using them in your daily tasks as a developer.

1. Visibility of System Status
2. Match Between System and The Real World
3. User Control and Freedom
4. Consistency and Standards
5. Error Prevention
6. Recognition or Recall
7. Flexibility and Efficency of Use
8. Aesthetic and Minimalist Design
9. Help Users Recognize, Diagnose and Recover from Errors.
10. Help and Documentation

http://www.usereffect.com/topic/25-point-website-usability-checklist