7. Don't Be A Tattletale
"Jack always takes an extra few minutes on his lunch break so he should stay behind after everyone else has left because that means that we're working harder than he is." Unless someone has participated in some serious gross misconduct, no one wants to hear it because it's silly things like that that are wasting everyone's time. If you have a problem, talk to the person first before going behind their backs and taking it higher. Being a tattletale is literally only acceptable if you're a spy for MI5 and you've discovered some Soviet secrets that could save the world, then yes, by all means, reveal everyone's misdemeanours.