1. Learn programming language as good as possible!
2. Use a style guide!
3. Use code analysis and profiling tools!
4. Apply clean code developer rules!
5. Apply common design patterns!
6. Write unit tests!
7. Apply the agile software development methodology
8. Use a source code control
9. Meet colleagues for code reviews!
10. Visit lectures and conferences!
And another tip:
Never be satisfied with ‘good’ code! There is always room for improvement!