I’m often asked: “when do I use mich and when do I use mir?” What at first seems to be a very straight forward question is unfortunately not that easy for many to get their heads around. The answer is that you need to understand the cases.
German has four cases: Nominative, Accustaive, dative and genitive. For the mich/mir question we are addressing the accusative and dative. The nominative you already have down when you use ich, du, er etc.
We’ve moved. You’ll find the full article here: http://marathonsprachen.com/mich-or-mir-accusative-vs-dative/