My favorite thing to do is go monarchy for the beginning of the game, conquer 2-4 civs depending on my position and luck, then work towards a democracy and Universal Suffrage. I usually work towards Military Tradition and trade for democracy. Sometimes I'm ahead enough in tech where I research democracy myself. By the time I have democracy, I'm usually finishing up a war with some civ that is down to 2-3 cities. If I'm not, I make an effort to finish it up quickly. Then I switch to democracy and shift to hardcore research mode. I usually beat or tie the computer to industrial age, and beat the computer to Industrialization. I often will palace pre build for Universal Suffrage because I feel it is extremely important for a warring civ (monarchy doesn't cut it anymore, and communism... well I have yet to develop a useful strategy involving communism). So then my next goal is to get Theory of Evolution, it's important if not vital in getting a clear cut tech lead on the computer at the beginning of the industrial age. Between industrialization and theory of evolution, I'm usually able to trade up to communism and build police stations in my core cities. I usually re-enter the cycle of war about midway through the industrial age, using infantry and artillery at first and then switching up to mass bombers and tanks.
Women's Suffrage and Police Stations usually prevent a whole lot of war weariness... I'm not sure if Democracy is more susceptible to War Weariness than Republic, so if you are into waging longer wars republic might be better. After my transition to industrial, when I wage war after that wars are usually fairly quick, 3-4 turns or less... I take some cities and negotiate peace. I've had games where I've been able to keep at war long enough to finish off 2 civs without any War Weariness on Regent.
I used to use republic for my switch and have never had huge problems with war weariness on regent. Using democracy is newer to me, I find it's really useful for early industrial when it comes time to landscape your nation with rails (workers work faster). Although I get lazy most of my games and win through space race, I think this type of strategy would still be sound for a domination or conquest type of game. My experience with Democracy as a gov't is limited I'm speculating a little bit, but I think police stations and Women's Suffrage will do a whole lot towards keeping a civ content while reducing an AI civ's competitive edge, keeping you ahead of the game.
I'd appreciate any comments anyone has about the differences between republic and democracy as war-time govs. I think the important part is that you really hafta aim at Women's Suff.
Hopefully i didn't exclude any major points, this post is getting long and my mind is wandering...