Matthias Noback, author of "Principles of Package Design", published the first article in a new series on programming best practices on the iBuildings blog. The subject of the first article is reducing complexity.
Inside your method or function bodies, reduce complexity as much as possible. A lower complexity leads to a lower mental burden for anyone who reads the code. Therefore, it will also reduce the number of misunderstandings about how the code works, how it can be modified, or how it should be fixed.