I am currently playing or have completed six World games, and I've seen a few patterns.
-Alliances-
Most World games that I've played become dominated by a handful of strong alliances, which jockey for the support of the other nations. Joining nations are then either incorporated into the alliance or eliminated once their usefulness has expired. Once only a single alliance remains, or the remaining alliances have made peace, the other nations are eliminated and the game is either drawn or the alliance turns on itself.
This, of course, is why talking to _everyone_ is important. Try to find a skilled and reliable ally early on, who needs not be a neighbor, and stick with them. Find a third, and you'll have a strong triple which can shape either global or regional events, depending on your relative positioning. If you notice other alliances forming, especially regional triples (the North American triple is deadly), either join them or work to break them apart by whatever means necessary. Once no other alliance can oppose yours (though getting a head start never hurts), position yourself so that it would be very difficult to cut you out of the draw. Alternatively, if there appears to be an opportunity, position yourself for the solo. If you can do both at once, all the better.
-Regions-
The World map is roughly divided up into regions, with some overlap between them. You've got South America, North America, Antarctica, Africa, the Mediterranean (Europe, Middle East, and North Africa), Asia, and the Pacific Islands.
In the first few years, the powers in each region tend to do one of either two things. Kill each other or make a lasting alliance. In the former, the larger team usually wins (2v1 is especially common, and effective, in North America). If two regional powers face off, the victor is usually the one who can bring in outside aid, or, all else being equal, stab first.
Pacific Islands is a unique region in that it is occupied by a single power, Oz. Consequently, a competent Oz very commonly survives the early game, but has more difficulty expanding. Oz needs to be opportunistic, achieving gains by intervening in other regions, or else they will likely be gobbled up once the other regions have settled. Probably the most common means of doing this is to work with South Africa to eliminate Frozen Antarctica, who himself must either make peace with Oz or find a way to stab him early, as a direct military confrontation rarely ends well.
If you can manage it, dominating your entire region will generally put you in a strong position. South America, especially, is a region that is difficult to defeat once controlled by a single nation. If you can't defeat your neighbors, forge strong alliances with them or lure in outside aid from less turbulent regions.
Finally, if you find yourself the runt of your region, appeal to everyone and their mother for aid. Hopefully, you will catch at least one opportunist. Stall until then by making your enemies fight over your corpse. And if all else fails, go into exile and hire yourself out as a mercenary. Greenland is a nice place for this.
Good luck!