Please consult the Cultural Protocols Index for more information on the cultural status of each nation.
To quote section 15.1 of the rules,
15.1.1 The simplest way to affirm a Cultural Protocol is to pass an OOC (out-of-character) "Motion of Cultural Protocol Affirmation" bill. To qualify as an affirmation, the bill must be supported by a 2/3rds majority of all players with seats (not just those with seats who vote) and over 50% of the seats in the legislature. Also, at least one of the players sponsoring the update must have been currently continuously active in the nation (ie. no inactivations) for at least 1 month. A link to the bill should then be posted on the Cultural Protocol Approvals thread.
A "Motion of Cultural Protocol Affirmation" can be as basic as this.
Affirmation can also be carried out through passing a Cultural Protocol update. For more detailed information on this process, please read sections 15 & 16 of the rules.