Ok. Here is what i generally do (especially with a religious civ). The way I play is more a builder game, and when i have wars, it is usually just the short, 20 turns or less. I generally try to make peace asap. (or until I destroy someone) I only go to war when either someone declares war on me, or one of my closer allies asks me to do so.
I research monarchy fairly early on, and make the switch from despotism as soon as possible. The reason for this is that monarchy is similar to despotism, but better. More military police and no negative food/production/economy.
I will stay in a monarchy until I feel I havea well developed nation. If I am a religous civ, i may include a change to republic, but generally I skip straight from monarchy to democracy. Before you make this switch you need to make sure you are well developed economically, as you will have no unit support in democracy, it'll all come out of the treasury. I find democracy the best for me because the bonuses to production (150%) and economy make it worth my while to change.
Just recently tho, i am beginning to change my playing style to deal with the added difficulty in monarch. I need to increase my military power. This means I stay in monarchy longer, and am starting to experiment with communism.
For communism to work you need to have
a) a large empire
b) hospitals in you major towns (towns <= 12 give you 4 unit support, towns >12 give you 8 unit support)
c) courthouses and police stations in most towns to reduce corruption.
communism means you can support a larger military. under communism, all corruption is shared, this means you don't have some huge production cities, and others with so much corruption they can't do anything. All cities will have similar corruption rates, so your outer fringe cities will be able to build, but your "main" cities won't have as much as they did.
Communism used to be crap because it had too much corruption, but one of the patches fixed it a bit, so i think it's feasible now, but still experimenting. I suggest you read about the governments in the Civilopedia, but more importantly, experiment with them in a difficulty level you can stand to see what works best for you.
Also sorry about the length. I got started and couldn't stop