One point I'd share is if the code is built in "modules," and when I say that I mean that you can change one thing in a module and easily have it working with the whole. It eliminates effects between unrelated things. Also:

• Code is easy to reuse
• Your code is flexible (this ties in with building in modules)
• DRY - Don't Repeat Yourself

I highly recommend reading, The Pragmatic Programmer.