This is not a rules page, however "proper" speech might add to the immersion and help you play a believable character, and keeping your character believable IS in the rules!
In medieval times, using the correct titles when addressing nobles, royalty, and the church was crucial for reasons of social hierarchy. Medieval society was highly layered, and titles reflected one's rank and status. Addressing someone incorrectly could be seen as a challenge to their authority or position. This guide is supposed to help you avoid awkward moments of not knowing how to address your betters and also to keep your head on your shoulders!
Proper titles were a matter of respect. Using the wrong title could offend whomever you were addressing and lead to repercussions in form of physical punishment (please, do not abuse this to kill people for not addressing you by all your fifteen titles).
Calling your betters by their title and title only (i.e.: King!! / Queen!! / Hand!!) is disrespectful and should be avoided. Nobles and Royals have names and they usually take pride in them! Use their names, or face the WHIP.
Monarchs
Children of the royal couple
Royals & Unlanded nobles
Priest & Clergy
Church is the legitimizing force behind the crown. It holds immense power and the Priest is appointed by the Holy See, personally. It is also worth mentioning that Clergy and the Priest are not expected to use terms of submission when addressing nobility and royalty, especially the Priest. Submitting before other rulers is seen as an undignified act and it is below the Church to do so.
This guide is a mere suggestion to how you may address the higher layers of the society. As stated prior, this is not the rules page, you may either embrace or ignore this guide and it is entirely your choice. Only thing that matters is that you roleplay and have fun doing it! Perhaps, I'll add more stuff into this guide later. If you have more ideas, feel free to ping @nik_nourse in monkeystation discord!
May the Ten be with Ye.