I love Risk... I'd play it a lot more, but it's always such a pain to find enough dedicate players. Anyway, I tend to have the most success by trying to hold S. America and Africa. Get whichever you can first, then go nuts getting the other, then figure out which is the best way to go after that. However, what I think is more fun is piling up in Europe, and trying to claim to everyone that you're just a buffer zone. Whenever you attack, assure them you're not planning on a war, but just keeping your little hold in the middle of the world safe. It only works once with each group of people though