Ethics can take a career to argue and about three seconds to decide in real life. So carry one question with you: what would the world look like if everyone did the thing you are about to do? It settles most situations quickly. A few people ask it, understand the answer perfectly well, and go ahead anyway. I have never seen that work out for them over time.
This is the short version. The full lesson, with the story behind it, is in the book.
Take The Summer Camp MBA with you, or get the field notes by email while you work through the lessons here.