Ethical Theory: Consequentialism, Deontology, Virtue Ethics and Meta-ethics
What you must understand
Consequentialism judges actions solely by outcomes; utilitarianism (Bentham, Mill) is its classic form, with act/rule and hedonistic/ideal distinctions. Know the utility principle, the difference between maximising total welfare and equal consideration of interests, and objections: justice, integrity, demandingness and the separateness of persons.
Deontology locates morality in duties and rules rather than results. Kant's categorical imperative has the formula of universal law and the formula of humanity (never treat persons merely as means). Understand hypothetical versus categorical imperatives, perfect and imperfect duties, and the critique that deontology is too rigid (the inquiring murderer, conflicting duties).
Virtue ethics (Aristotle) focuses on character, eudaimonia, the doctrine of the mean, practical wisdom (phronesis) and habituation. Its weakness is action-guidance and potential relativism.
In meta-ethics, distinguish cognitivism from non-cognitivism (emotivism, prescriptivism), moral realism from anti-realism, and the is/ought gap (Hume). Understand moral relativism, subjectivism and error theory, and the naturalistic fallacy.
Traps
Don't label any outcome-based view 'utilitarian' automatically. Don't confuse meta-ethics (what moral language means) with normative ethics (what we ought to do). A frequent trap is attributing rule-worship to Kant or ignoring Mill's harm principle.
Rule of thumb
Ask: what is the theory's criterion of rightness? Then test it against a hard case, and always state the strongest objection plus a possible reply.