I look at the most promising putative moral theories. I construct crucial thought experiments in areas where they give conflicting advice. I confront their conflicting advice with my own moral sensitivity, my moral intuition. I take the theory that can best explain the content of my intuitions as gaining inductive support through an inference to the best explanation.
The only good teachers for you are those friends who love you, who think you are interesting, or very important, or wonderfully funny.