Royalty
Queen/King: Her Majesty; "Your Majesty"
Princess/Prince: Her/His Highness; "Your Highness"
Queensman: His Honour; "Your Honour"
(Note: The Queensman is not royalty, but he's part of the royal household and is treated as such.)

Nobility
Duchess/Duke: Her/His Grace, "Your Grace"
Countess/Earl: Her/His Ladyship/Lordship; "Your Ladyship/Lordship"
Baroness/Baron: Her/His Ladyship/Lordship, "My lady/lord"
Children of nobility would refer to their parents as "my lady mother" or "my lord father". The children of nobility would not be referred to by any term of address except for "Master" and "Mistress", although an adult child might be called "my lady" or "my lord" out of respect.

Baird
Master baird or banded baird: Master [Surname] (even if they're female)
Journeymen baird: Sire/Mistress (or just by name)
Anybody else: By name, or as lord/lady as a term of respect
There is only one High Bard of the College at a time. Currently, it is Aisling. Her formal title is "High Bard Aisling," but most baird would refer to her, informally, by name.
(Note: the plural of "bard" is "baird," but it's cool to refer to them as "bards" in-game.)

Guards
Guard captain: Captain
Regular guards: Sire/Mistress (or by name), or just Guard plus a surname if you know it. Or just "guard".

Knights
Sir/Lady Knight, or Sir/Lady [Surname]. Bear in mind that not all guards are knights and not all knights are guards.

A general rule is that anyone who is dressed better than you, but whose rank you do not know, can be called "my lord" or "my lady" without too much fuss. They'll likely correct you pretty quickly.