Depends on your age. If you are in college, taking an introductory course or two on ethics and metaphysics could be useful. If that's not possible or realistic,

Depends on your age. If you are in college, taking an introductory course or two on ethics and metaphysics could be useful. If that's not possible or realistic, Nicomachean Ethics, A Critique of Pure Reason, and Utilitarianism were the most useful classic philosophy texts I have read, and should be available on the internet and in most large public libraries. Be warned however that all can be quite daunting, companion books could be useful if you do not have a professor or TA to provide context.