
Basically...you go to get a promotion at any shrine at least once every game

Depending on what 'Medals' you acquire along the way, it will give you more "promotion options" to choose from when you do. Just make sure to 'read those books' to get an idea of who can get a promotion. If the person in your party doesn't show any options, then he/she is done.
MM4 has a change, to gather whatever 'Medals' you can find

You'd be amazed at the options
