Tomoyo said:
What do mean "not as good economically as democracy"? They have the same bonus! If you're talking about corruption, I'll counter with the extra revolution...
Democracy also gives a production bonus, which is pretty awesome. Corruption is also less. You lose a few turns switching, but you'll have two entire ages to reap the benefits. Only way democracy isnt the best is in war, and then, unless you are going to be at war absolutely nonstop, Republic's war weariness isnt very bad at all.
I tend to go Despotism->Republic->Democracy
If religious, I might switch more later if going to war, but generally I'll just try to have short wars where I take some stuff and then get peace and more stuff in the peace deal, then repeat a bit later.
I tend to try and run at a minimum of 70% science, often up to 100%, from the Middle Ages on. Usually, my GPT from the AIs is more than all my expenses. This is in C3C, Deity difficulty.
I go for the paths the AIs dont go for as much, and swap and get GPT. For example, in Middle Ages, I ignore the bottom half, and go for Monotheism, Theology, Education, Democracy, etc...
I'll be swapping these for the more miliaristic techs in the bottom half, and then I'll tend to do the techs like Magnetism at the end.
In Modern Age, I get steam power for railroads, and go up the replacable parts track while they are all messing around with Nationalism and Communism and stuff. I go for Industrialization, Corporation, etc, all the way to Tanks. I try to get Darwin, giving 2 techs (generally Refining + Steel, I find). I try to hit Tanks 3-4 techs ahead, and start a modern war with them, in which I take some cities quick, and then go into peace as soon as they will talk to me (for more stuff), then repeat a bit later. I'm in democracy the whole time, so I dont want to let the war weariness build up too high.