How To

General
There are some general things about sending mail that are specific to your country (I.e stamps, where things go on the envelope, etc.). Your country's national postal service website should help answer these country-specific questions.
Sample letters/cards to the Royals: 
If you would like to submit your own letter/card, email me at gertsroyals@gmail.com or direct message me on Twitter, Facebook, or Instagram. I will pick a few of the best that represent a range of styles for the more formal to informal, personal, creative, long, short, etc. And I will remove any sensitive personal information like your address, last name, (First name too if you want), etc.