A few obvious and maybe not so obvious sources of valour:

Virtues and vices add to the valour primarily of the general. For instance Pride adds something like +3 valour to the general... while hampering his command by reducing his stars by two. This is a good general to use in small battles as he will carry the day single handly with pride

Every 2 stars of the general add one valour to your troops. For instance a six star general adds +3 valour to all his troops.


Some provinces will add +1 valour to a particular unit built their. For instance Longbowmen built in Wales get +1 valour

Having the maximum (master version) of a building of the right type will add +1 valour. For instance hobilars built in a province with a master horse farm will get +1 valour.