I think everyone covered the continents trick quite well, just take over everyone in your continent before you meet the other continents. As for Pangaea I have a couple of quirky tips that work pretty well:
If there are any warmongers or just plain powerful civs, just bribe them into attacking a neighbor or even better, a city state. They normally win the war and get a huge diplo hit and everyone hates them. Makes it easier for you to get a coalition to destroy them and you can take their capital then liberate the city state for only a minor diplo hit.
If the warmonger attacks another civ, make sure they wipe out the other civ. That way when u attack the warmonger, you get two capitals and then you can bring back the conquered civ in a minor city. If you do this to one warmonger it's very helpful, if you manage to get a warmonger to take two civs, then it's a downright cake walk. The revived civs will never be significant to bother you later on, and they'll put up with a lot more of your warmongering than the other civs. Also once you get into late game and are gobbling up cities in quick succession, you can gift the lesser cities to your revived buddies and they'll either raze em for you or puppet them, either way the happiness penalty is off your hands.
Speaking of happiness, always get into big coalition wars and (like I keep saying, make em happen if they don't happen naturally) stay at war, even if tbe war is going on somewhere far from you. You don't get any more warmonger penalty for staying at war for longer period. Once the enemy is willing to give you all their treasury (in the late game this can be immense sums, like enough to buy a whole spaceship) or all their cities. When they give you their cities, just sell them off to the highest bidder or gift them to the weakest power. Usually the weakest power is so weak, a couple shiny, new cities will be irrelevant to their influence in the world.
Also if the Huns are in the game, make them ur ally and give them cities you conquer that you don't want. They'll stick with you even through all your warmongering, basically until the end, and they'll burn all the cities you gift them extra quick, making your campaign that much more efficient.
Summary: Trick the AI by instigating warmongers, liberate their conquest but keep capitals, force every war to end with either their whole treasury or their cities, sell/gift all non-essential cities.
