Rubber Ducking
Don't underestimate the value of Rubber Duck Debugging.
When you're trying to make sense of a problem, talk it out. Even if that's just to a rubber duck that you keep on your desk.
Try it. You'll be amazed at how often it leads you to think of something you've overlooked.
Next Up:
Fear of Failure Leads to Failure
Previously:
Don't Forget the Obvious