Rules of etiquette, or rules for making the tea taste better?
There's lots of both, and you can always find one rule to contradict another.
For making it taste better, brewing good tea is kind of like baking; there is some precision chemistry involved, so following someone else's recipe exactly is a good idea unless you have a fair bit of experience, enough to know where there is wiggle room. For example, as with baking, the wrong temperature can get you an unholy mess.
I used to be doubtful that the material of a teapot could make the difference in the taste of the tea that some people said it would, until I confirmed it by experiment. Then I realized that I'd known from experience since childhood that the material of a baking pan could make a big difference in a cake, so I don't know what my problem was believing teapot material is just as important.
I feel like I'm pimping Teamasters everywhere today, but that's the blog that got me off and rolling on making good tea.