I have a guest post, Lesson in Software from Mike de Libero, on Shaping Software.  Mike was a security tester on the Microsoft Office team and has a variety of experiences under his belt.   Here is a summary of his lessons:

• Lesson 1. All software is flawed.
• Lesson 2. Check-in often.
• Lesson 3. Tests, gotta love them.
• Lesson 4. Refactor, check-in and repeat.
• Lesson 5. Coding is easy, humans are tough.
• Lesson 6. The more eyes on your code the better.
• Lesson 7. Keep learning and improving.
• Lesson 8. Simple is beautiful.
• Lesson 9. Learn software development not coding.
• Lesson 10. Think about your audience.

You can read an explanation of the lessons in his post, Lesson in Software from Mike de Libero.