Being a good friend is about having trust in your friend and being trustworthy, in all friendships people are bound to say bad things behind the others back, but being able to overcome that is what makes a good friendship. Another thing to being a good friend is the small things in that friendship, and what I mean by small things are maybe inside jokes that only you and the person know about ( BrO FlINCH, Six, Paradise, Juat, Dr.Phil), or maybe just doing something nice like picking them up a coffee before school. Doing small nice things make friendships stronger. Being a good friend is about caring about your friends feelings, enjoying their company and liking to be there for them.
Even though it’s contradicting writing the unwritten rules of friendship, I suppose I’ll list some anyways. You should never intentionally do something to hurt your friend, because if you do what kind of friend are you? You should always do something for them on their birthday whether it costs money or not. If they need help with something, try and be there for them. And to me the most important rule of friendship is listening to your friends problems and trying to help them with them, but with great power comes great responsibility you should keep the secrets they share with you to yourself.