To tutor writing, you also have to have a good grasp on what sort of language, terminology, and tone is appropriate given the context. For example, research papers tend to be much more formal and technical in tone than literary analysis or personal reflection essays.

In order to validate that my instruction was understood, I always ensured that my students could apply these principles without explicitly telling them what to do. 

From a UX perspective, you could say that  my earliest "user groups" were the students I was instructing and the educators reading and grading their work. If the student saw an improvement in their grades after coming to me for help, I considered it a win for everybody!