I also use the Recruitment Viewer to identify one settlement in each area that I'm pacifying to be the source of my local troops. Usually I have one for every 6-8 "non-military" regions. I choose one that has a good range of local troops available, and is fairly close to all of the neighbouring regions that it will be providing security for.

This allows me to focus the other regions on developing their economies, while the military one can focus on MICs (and blacksmiths, military temples). For the military settlements I go for a level 4 government, as I can build the best MICs (and so get the best regional soldiers), and I find that the client rulers tend to keep these pretty stable for a decent while. The ability to recruit generals is always handy, and they can then hire mecenaries as a last resort if things get really tight.

Any non-military settlement is singularly focussed on making me money, so I go for the highest level government possible. I keep garrisons to a minimum (to save costs), and defences are just enough to hold off attackers until help can come from my "protector" cities.