What protocol is advised when meeting the Queen?

The Queen’s representative in Canada had had a brush with controversy after helping the monarch down some stairs.
David Johnston, the Governor General of Canada, admitted breaking royal protocol by touching the arm of Queen Elizabeth II as she descended red-carpeted steps outside London’s Canada House.
Johnston told CBC News he was aware of the protocol but breached it to prevent the queen from stumbling as the carpet outside Canada House was slippery.
The Royal Family’s official website states that “there are no obligatory codes of behaviour when meeting the Queen or a member of the Royal Family,” but here are some rules anyone coming into contact with British royalty might like to follow.
Touching a memeber of the Royal Family
The website says members of the Royal Family should not be touched in a manner that goes beyond a formal handshake (a principle likely dating back to the Middle Ages).
Greeting a member of the Royal Family
Men should neck bow – from the head only – whilst women should execute a small curtsy. Some people prefer simply to shake hands, which is acceptable according to the Royal Family’s official website.
When presented to the Queen, the correct formal address is ‘Your Majesty’ and subsequently ‘Ma’am’.
For other female members of the Royal Family ‘Your Royal Highness’ should be used when being presented and and subsequently ‘Ma’am’.
Concerning male members of the Royal Family, ‘Your Royal Highness’ should be used during a first meeting and subsequently ‘Sir’.
Dining with the Queen
It is generally considered good etiquette to follow the Queen’s lead when dining with her. Once she has finished eating, so should those around her, including other royals.
Guidelines for the royals
The Royal Family are also expected to follow codes of behaviour, although some are now outdated.