Like the topic name suggests post and discuss your strategies.
For me I stick to one general strategy that works the majority of the time, in which I start in (starting territories allowing) either Africa, South America, or Antarctica (in order of preference). After taking my first continent I look around at the map and find easy targets in the other Southern continents. I then attack them and take the continent they're on generally in a short number of turns.
If that all goes well I normally have the entire Southern half of the world, from which I get into a large war with the Northern half, which I fight mostly at sea for the main war, after a while it devolves into land combat and I eventually win. My record fastest game using this strategy is 14 turns.
However, when the strategy does not work it can devolve quickly, most of the time though if you act quickly you can salvage the game, but it'll take a lot longer than 14 turns.
Psst the secret, and this isn't the most... sporty thing to do is to watch the map just after taking your continent, most people will be fighting for their continent still, when someone seems about to take their continent it's the time to strike.
DOUBLE PSST IF YOU SEE THIS IT'S OUR SECRET