Philosophy of Religion: Arguments, Faith and the Problem of Evil
What you must understand
Know the classic arguments for God's existence. The ontological argument (Anselm, Descartes) moves from the concept of a greatest conceivable being to its existence; Kant's objection is that existence is not a predicate. The cosmological argument (Aquinas, Leibniz) argues from contingency or causation to a necessary being; Hume and Russell question the principle of sufficient reason and demand an explanation of God. The teleological argument reasons from apparent design; Hume's criticism and Darwinian evolution are central.
Understand the problem of evil: the logical problem (Mackie) claims evil is incompatible with an omnipotent, omniscient, omnibenevolent God, while the evidential problem (Rowe) claims evil makes God's existence improbable. Know theodicies: free will defence, soul-making (Irenaeus, Hick), and the greater-goods response, and the distinction between moral and natural evil.
On faith and reason, compare fideism, natural theology and reformed epistemology. Understand Pascal's wager and its criticisms.
Traps
Don't confuse the logical and evidential problems of evil; the logical form is widely thought to have been answered by the free will defence, while the evidential form persists. Don't treat the ontological argument as an empirical inference. Avoid asserting God's existence or non-existence as settled-questions ask for evaluation.
Rule of thumb
For each argument, state the premises, the inference, then the strongest objection and a possible reply.