We compost everything possible, emptying it into a homemade compost bin and covered with an old carpet. The carpet serves two purposes: one extra heat, two cats like sitting on it and so deter rats etc. Incidentally apparently its unwise to compost either apples or parsnips as both are favoured by rats.
As for garlic, planted randomly amongst lettuces etc it helps deter rabbits.
French marigolds help with aphids as does a plant nicknamed Fried Egg Plant (I don't remember its proper name)