My best subject to tutor in is math or physics. Once you know how to break down a problem into its parts and learn to recognize them, all numbers and equations start to unravel themselves for you. My degree is in molecular biology but I have taken classes across a broad spectrum from literature to history to chemistry to calculus to biological writing. I personally learn best using hands on models and try to tutor by explaining problems as interactively and concisely as possible. You have to know all the little steps before you can begin make giant leaps between ideas or within solutions!