History of Philosophy: Ancient, Medieval, Modern, and Contemporary Thought
Ancient and medieval
Know the Presocratics (Thales, Heraclitus, Parmenides), Socrates (elenchus, the examined life), Plato (Forms, the cave, the tripartite soul), Aristotle (four causes, virtue, logic), Plotinus (emanation), and the medieval synthesis: Augustine (faith and reason, the city of God), Aquinas (five ways, natural law), Ockham (nominalism).
Modern
Know Descartes (method of doubt, cogito, dualism), Spinoza (monism), Leibniz (monads), Locke, Berkeley, Hume (empiricism and its limits), Kant (Copernican revolution, synthetic a priori, categorical imperative), and Hegel (dialectic, absolute spirit).
Contemporary
Know phenomenology (Husserl), existentialism (Heidegger, Sartre), analytic philosophy (Frege, Russell, Wittgenstein), pragmatism (Peirce, James, Dewey), and critical theory (Frankfurt School).
Traps
(a) Attributing the theory of Forms to Aristotle; (b) confusing Hume's empiricism with Berkeley's idealism; (c) treating Kant's a priori as innate ideas; (d) placing existentialism in the ancient period.
Rule of thumb
For any historical question, anchor the thinker in period, problem, and key concept - then state the position in one sentence before evaluating it.
Worked example: "Who claimed that the mind is a blank slate?" - Locke (empiricism). The trap is answering Descartes, who held innate ideas. Anchor by period and school.