Here are my favorite principles of logic and reasoning, collected from Leonard Peikoff’s Objectivism: the Philosophy of Ayn Rand.
While these do stand on their own, they become most useful if you study them individually and in depth. For that, I recommend Peikoff’s book.
1. All our knowledge is based on observation and logic.
2. Logic is the art of non-contradictory identification.
3. Always ask, “What facts of reality give rise to our need for this concept?”
4. To think in essentials, ask, “On what fundamental principle does this question depend?”
5. Check your premises.
6. Avoid stolen concepts—no concept can contradict an earlier concept on which it depends.
7. Any statement is true, false, or arbitrary.
8. An arbitrary statement makes no attempt to connect with observation, so it cannot be evaluated.
9. Certainty is contextual. We may say, “Given these observations, I am certain that this conclusion follows.”
10. Disinterest is not a feature of objectivity.