The curious thing is that you will never be able to write a set rule or protocol on deciding who gets to be in the First Class, it's instinctual. You meet someone, exchange pleasantries, then they start to seat themselves into the different classes. Most people will gladly stay in the Economy Class, but once in a blue moon, you will bump into another person who you will invite to the First Class straight away.
Sometimes when you arrive at certain airports in life, some of the passengers may depart and new ones will board. Even your First Class passengers may leave you in pursuit of their own destination, but you'd always reserve an empty seat for them. For you know that someday when they'd like to fly with you again, there is always a seat for them.