Taking from the last longer piece and a very good idea that @codePrincess linked to in a blog post: Code that says what it does. Of course, source code also is a medium of communication between human and human – but the person you are writing for may just be the future you. And just as the user interface is an act of communications, so is your source code.
Do you want to impress the reader with your skills in optimizing, but producing hard that is extremely hard to read? Do you want to be considerate and share a lot of your thought process in your code, or is it better to have the reader guessing as to why you chose a particular road to implementation? Try to be nice to somebody who will have to live with your code later on – it just may be yourself!