Do not interrupt. No unnecessary interruptions (or whining or arguing) is allowed when grown-ups are having a conversation. If it is urgent, then ‘excuse me please’ should do the trick.
Minding others’ space. Both at home and outside. For instance, knocking on someone’s door and waiting for a response before entering is a must.
No making fun of others. I always teach my kids that making fun of others or calling them mean names is wrong. When you point one finger at someone, there are three fingers pointing back at you.
Covering their mouths while coughing or sneezing. This is something both the kids have gotten used to by now, since they’ve seen their parents doing it forever.
Hope these manners stand them in good stead all through their lives!