[nihonde]

No one is going to get mad at you for violating these, but they will judge you. If you're trying to get along with a person from a proper Japanese family, you'll fail unless you know all of these and more. For example, placing bowls/plates on the table too hard, or not trying hard enough to pay the bill, not serving others, pouring your own drink...the list goes on and on. Most people think these things are silly, but some absolutely do not and will treat you accordingly if you're making these mistakes. Whether or not you care is up to you and the situation. This is all also true in almost every other culture, by the way.