Forms of Address Along with the Titles and Coronets of Peerages the are differing forms of address. So in the hope of also making this clear, this is How to Address Peers

King & Queen:	are address as	Your Majesty
Prince & Princess:	are address as	Your Highness
Duke & Duchess:	are address as	Your Grace
Margrave & Marquess:	are address as	Your Grace
Earl & Count & Countess:	are address as	Your Excellency
Visscount & Visscountess:	are address as	Your Excellency
Baron & Baroness:	are address as	Your Excellency*
Knights:	are address as	Sir, Lady or Dame
Laurels & Pelicans:	are address as	Master, Mistress or Dame

*May vary by location, Landed barons can be called "Baron(ess) (Place name)" Landless barons can be called "Baron(ess) (their name)"

Note too that it is acceptable to address anyone you meet as
My Lord or My Lady
This works fine in every address situation
and it's very hard to get it wrong.