On presentation to The Queen, the correct formal address is 'Your Majesty' and subsequently 'Ma'am,' pronounced with a short 'a,' as in 'jam'. For male members of the Royal Family the same rules apply, with the title used in the first instance being 'Your Royal Highness' and subsequently 'Sir'.
Open correspondence with 'Sir' and close with 'I have the honour to be, Sir, Your Majesty's humble and obedient servant'. His Royal Highness The Prince first name, Earl of …
Address The King properly. Your Majesty or May it please Your Majesty are the preferred terms. While it may be more appropriate to address His Majesty's Private Secretary or, you can direct the correspondence to The King. The Royal family also accepts the less formal Sir” substitution.
For men this is a neck bow (from the head only) whilst women do a small curtsy. Other people prefer simply to shake hands in the usual way. On presentation to The King or Queen, the correct formal address is 'Your Majesty' and subsequently 'Sir' or 'Ma'am,' pronounced with a short 'a,' as in 'jam'.
In Writing Envelope: The Private Secretary to The King (for example). For those who do wish to write directly to The King, the letter should begin 'Sir' or 'May it please Your Majesty'. It ends with 'I have the honour to remain, Sir, Your Majesty's most humble and obedient subject' and then your name.
If communicating directly with a member of the Royal Family the letter should begin 'Sir/Madam' and end 'I have the honour to remain, Sir/Madam, Your Royal Highness's most humble and obedient servant'. In the body of the letter substitute 'Your Royal Highness' for 'you' and 'Your Royal Highness's' for 'your'.
Bow or curtsy if you are a subject of the royalty. If you're a citizen of the country where the person is royalty, show your fealty by bowing or curtsying. If you're a man, give a slight nod of their head, but don't bow with your whole body. Women, give a brief curtsy.
In conversation, refer to 'His/Her Majesty' or 'The King/Queen', as appropriate. 'Your Majesty' should be substituted for 'you'. References to other members of the Royal Family are made to 'His (or Her) Royal Highness' or the appropriate title, such as The Princess Royal.