Humans routinely assess thinking – their own thinking, and that of others, and yet they don’t necessarily use standards for thought that are reasonable, rational, sound. To think well, people need to routinely meet intellectual standards, standards of clarity, precision, accuracy, relevance, depth, logic, and so forth. In this guide we offer a brief analysis of some of the most important intellectual standards in the English language. We look at their opposites. We argue for their contextualization within subjects and disciplines. And, we call attention to the forces that undermine their skilled use in thinking well.