- King or Queen: "Your Majesty"
- Hereditary Prince or Princess who rules a principality: "Your Royal Highness"
- Crown Prince or Princess in line for the throne: "Your Royal Highness"
- Princes or Princesses who will not inherit: "Your Highness"
- Dukes: "Your Grace"
- Barons, Counts and Viscounts: "Your Excellency"
- Lords & Ladies: "Your Lordship or Ladyship"
- Untitled Nobles: "My Lord or Lady"
- Knight, Baronet: "Sir" "Dame"
Now you have the correct Honorific for addressing your superiors, but successful court etiquette is more than just getting the title right. History shows us that the rules of Royal Courts were often incredibly intricate and only the leisured classes could hope to master them. For the purposes of roleplaying the following examples are the distilled version of the rulebook and will help to give your encounters a more authentic feel.
Whatever you do, do not sit down if an out-ranking noble is standing in the room. Always bow or curtsy to a ranking noble upon arriving, leaving, or being acknowledged by them for the first time. Failure to do so is a terrible insult and depending on the nature of the lord can lead to isolation, duels of honour or even execution! Always ask permission to speak before conversing with someone of superior rank. Never interrupt a noble when they are speaking and if they interrupt you, fall silent immediately and wait for them to finish.
Games like D&D are usually set in a semi feudal society and most Player Characters start with humble origins. If this is the case then the best and most universal rule you can learn is simply this... remember your place!