TRIZ - A powerful methodology for creative problem-solving
The Straw Man Concept - Build it up, knock it down, create a solid final solution
5 Whys - Getting quickly to the root of a problem
Root Cause Analysis - Tracing a problem to its origins
CATWOE - Understanding the different elements that contribute to a problem*
Inductive Reasoning - Drawing good generalized conclusions*
Avoiding Logical Fallacies - What they are, and how to avoid them*
Critical Thinking - Developing the skills for successful thinking*
The Ladder of Inference - Avoiding "jumping to conclusions"*
Blindspot Analysis - Avoiding common "fatal flaws" in decision making*

from Habits of Mind