Don't. Waste. Time.
When it comes to efficiency/effectiveness, I prefer to focus on "Do" instead of "Don't".Richard Hamming (from "You and Your Research"):  1. What are the most important problems in your field?
  2. Are you working on one of them?
  3. Why not?

http://www.paulgraham.com/hamming.htmlPaul Graham's (from "Good and Bad Procrastination") generalization of Richard Hamming:What's the best thing you could be working on, and why aren't you?http://www.paulgraham.com/procrastination.htmledw519's generalization of Paul Graham:Work on the most important thing until it's not the most important thing any more.I have developed this excellent/horrible habit of not being able to focus on very much of anything if there was something more important hanging over my head.Excellent in keeping me from trivial pursuits. Horrible at meal time, bed time, other people time. I'm still a work in progress.