The first thing I would say is that when you write a program, think of it primarily as a work of literature. You're trying to write something that human beings are going to read. Don't think of it primarily as something a computer is going to follow. The more effective you are at making your program readable, the more effective it's going to be: You'll understand it today, you'll understand it next week, and your successors who are going to maintain and modify it will understand it.
From an interview in Dr. Dobb's Journal, April 1996. This was in response to the question, "If you could climb in the pulpit and scold, exhort, and encourage every working programmer in the United States, what would you tell them?"