A Critical Thinking Tool-kit and Guide to Baloney Detection from
The Demon-Haunted World by Carl Sagan

The following (from Thomas Kida's Don't Believe Everything You Think) are a useful set of characteristics of thinking like a scientist:

The next are Carl Sagan's Toolkit:

1. Independent confirmation of facts: In science, observations need to be both repeatable, and repeated.

2. Substantive debate by knowledgeable proponents of all points of view: No good comes when an authority silences substantive debate on an issue.

3. There are no true authority figures: Scientific discourse takes place on a level playing field in which ideas are judged by their merits Summed up in this bathroom graffito: "Ideas by merit, not by source."

4. Use more than one hypothesis: There are often many possible patterns or explanations for patterns. They should all be examined, and the quickest way to get to the answer is usually to examine them simultaneously and not to assume that they are mutually exclusive.

5. Don't get too attached to your hypotheses: The whole point of testing a hypothesis is to try to falsify it. If we don't try in earnest, then we really haven't done much. Alas, the world, including the scientific world, contains true-believers who could never, under any circumstance, be convinced that they are wrong.

6. Quantify: Remember, subjective observations are useless to science. Sometimes, subjectivity can creep into even detailed observations. The true proof of objectivity is often the ability to count or measure.

7. A chain is as strong as its weakest link: When your argument requires a chain of logical steps, each step must be valid or the whole thing is hogwash.

8. Parsimony (AKA Occam's Razor): When there are more than one possible solutions, the simplest one will usually be correct.

9. And the really big one, Falsifiability: In science you have to have a definite answer to the question, "If I were wrong, how would I know it?" If you don't, you aren't doing science. That means it must be possible, in principle, to know if your hypothesis is wrong. If you have no way of knowing if you are wrong, there's really not much to test or discuss scientifically.