Don't Use Second Person ("You")
An important element of good academic style is to stay away from the informal, colloquial use of second person ("you").
It's very common to slip into second person in every day speech ("Well, after you get to the corner, you need to turn left onto the freeway access lane.") Here, the "you" isn't referring to a specific person as much as anyone who needs to know how to get somewhere.
Whenever a student is writing in process mode (telling an audience how to do something, or how something is done), slipping into second person is a common mistake.
Students should carefully check papers before turning them in for incorrect use of second person by circling every instance of "you" in the paper, then correcting misuse of "you" by changing the sentence so that it is written in third person (he, she, it, they).