There are 5 requirements for joining. All these reasons have OOC reasons, but they have been translated into reasonable RP reasons.
1. Willing to obey orders.
2. Willing to wear a uniform
3. Register
4. Testing(Defeat fallen soldier and knowledge test plus any test the unit feels is neccesary)
5. Willing to be active majority of the time. (OOC requirement) The player must play his guard character majority of the time. If he is not going to play it then he must retire his character from the guard.