None of these are game rules. They are the social arrangements that took our group from "we should play more" to actually playing most weeks for four years.
If explaining takes longer than fifteen minutes, the game does not go on a weeknight. We learned this after a session where the rules took longer than the game.
Advice is offered when asked for, not narrated over someone's shoulder. Losing your first game while making your own decisions is the point.
One person checking a score is fine. Four people scrolling means the game was the wrong choice, and that is on whoever picked it.
If a game has stopped being fun ninety minutes in, saying so is allowed and not a failure. We finish maybe four out of five heavy games.
Learned expensively. A sleeve of cards is cheaper than a replacement board, and grease does not come out of linen bags.
Say what winning looks like before anything else. Everything else is easier once people know what they are aiming at.
Do not explain exceptions during the overview. Teach the standard turn; handle edge cases when they occur.
Play one open round where everyone can see each other's hands and take advice. It costs five minutes and saves a spoiled first game.
Hand out the reference cards. People who read them will; people who will not are not helped by hearing it twice.