Midterm help? It is so hard!?

I am taking a midterm on Political Philosophy and the Enlightenment. It will discuss John Locke, Hobbes, Voltaire, Galileo, Kant, Rousseau, Machiavelli, Treatise of the Three Imposters, Descartes, Newton, Diderot, Buffon and Montesquieu. I don't know what I need. I just need help in general. Any advice/website/method... anything!