unless you plan a very precise win in the AA get out of despotism as soon as you can.
monarchy only for always war, as others have said. this doesn't mean a game with alot of wars, republic can work fine for that, this means a game of always war - meet a civ, declare war, no peace until defeat.
republic is the gov't of choice for most of the top players. it is easily the most balanced. the greatest benefit is the one extra gold for each square already producing one. it is a bit difficult to adjust to with the unit cost and no military happiness, but learn to use it and it will absolutely be the best way to go. the trick is to build plenty of roads. have some workers assigned to this task exclusively. every citizen should be working a tile with a road as soon as you can complete one. roads, roads, roads!! this helps your tech rate, unit support, and happiness by providing the gold.
it has been shown that for 100k games feudalism is very effective.
personally i hate democracy. wasting research to get to it, and the costs for being a democracy are too great for the small benefit. i haven't noticed the increased production like it says in the civlopedia, (maybe one shield per city?). by that time you should have most of your productive cities improved, and roads to other civs completed the extra worker speed doesn't add much to your game. considering the extra anarchy don't even bother with democracy. going here straight from despotism is just a total waste.
i have tried communism a few times with very large empires. there is greater overall production, but i mainly dislike forced labor. whipping citizens late in the game doesn't seem benefitial. with other gov'ts i can cash rush and produce units as quickly, then after you have replaceable parts use the engineer specialist to help with improvements drastically off-setting waste and minimizing the benefit of communism. i don't think it is a useless gov't, but most victories can be had as easily by skipping it especially if you have only a modest empire.
i have never tried fascism, and see no use for it.
basically, unless you have a unique reason not to, get to republic as fast as possible, and stay there. if the game is played properly WW is easily managed, the unit support, and happiness are soon not an issue once your empire grows. use the slingshot for emperor games or below almost every time. even higher levels under the right circumstances.
get less anarchy: this is an allowed exploit. after you discover your gov't tech a pop-up will suggest what to research next. you are given the option to change the tech with the pull down menu, to agree with the suggestion, or to get the big picture. select get the big picture. this will take you to the tech tree. now press f1. this takes you to the domestic advisor. a small box with gov't type will be located below the sliders. click on the box. it will ask if you really want to do this. say yes. now check the advisor by clicking the word more. do this until the advisor tells you how long your anarchy will be. (it is not essential that you check for anarchy, but i just do). exit this screen. a pop-up will now ask if you want to revolt. say yes. and when you check the domestic advisor again you will notice one less turn of anarchy. you will see this mentioned in some posts as the big picture method of changing gov'ts. i have heard that it gives a new random number for anarchy, but in my experience it always results in one less turn. it only works if you discover the tech yourself. no huts or trades will permit a look at the big picture.