I have played Risk for a while and I I use the Australlia method, but there is one minnor flaw; move slowly on Asia. I once took over half the world in one turn from Australlia, but the other players counter attacked me and i soon died coming in second. If you have Australia and are trying to take over Asia, build an army of about 20 to 30 (you get 5 armies a turn so it takes 4-6 turns to do so) and take over 2-4 countries at a time. Fortify so each country has equal forces. Keep on doing this and you have a secure hold on Asia.