I find the this-many-points version confusing, so here’s what I told a newbie today, and he liked it, so I’m sharing.
Ladies and Lords might not wear hats, or may wear circlets. My lord and my lady are never impolite.
Duchesses and their Dukes wear hats with strawberry leaves and answer to Your Grace, but they usually have the grace to take an accidental demotion with dignity.
The Queen, King, and Their heirs wear hats with crescents on them (in Caid. Your royalty may vary). The King and Queen are Their Majesties, and heirs (princes and princesses) are Highness.
Everyone else is Your Excellency. This covers barony (who may or may not be in charge of anything), county, and viscounty. If you call a lord or lady Excellency, they’ll be flattered, and if you call anyone else Excellency they’ll probably be nice about it.
Non-Caidan royalty can be spotted because they have a hat and a retinue. A lady with a hat who does not hold her own parasol can generally be assumed to be a queen.