It makes you look ugly. And don’t talk into your watch. It makes you look crazy. What else?
Don’t wear a t-shirt that says, “I’ve got mad Ninja skills.” Obviously you don’t, because I can see you.
Don’t read instructions. You will lose your only excuse for doing it wrong.
Don’t take career advice from an overweight middle aged man with a scraggly beard and a ponytail, who is wearing a Star Wars shirt. Unless it’s George Lucas, having more than half of those things is reason to disqualify. Teacher by Day, Jedi by Night. I don’t believe he is a real teacher; a gym teacher, maybe.
Don’t eavesdrop on other people’s conversations. You might not like what they are saying.