Rules are useful guideposts that help us all dress better. It’s a good idea to adhere to what’s worked for generations of men and then, over years, alter rules that don’t apply to your build, your personality or your world view. Breaking rules should be done from a position of strength and not all that often.
I remember seeing photos of Luciano Barbera when I was young. Like many people, I wanted to dress like he did. He had heard this many times and said (and I’m paraphrasing), People ask me, How can I dress like you? Well, it takes a long time to do this. You don’t do it overnight. He might have added that it also helps to be Italian and to own your own clothing company.
For the rest of us here are some rules that follow traditions of proportion and common sense.