What can be done to prevent refugees from coming to Australia?
In many ways, there is little Australia can do to prevent refugees from coming. Most refugees are fleeing from countries like Afghanistan where there is war and poverty. Australia cannot do much in the short term to fix these problems.
If you are talking about the issue of refugees arriving by boat, one thing that Australia could do would be to implement a policy where it would not consider any applications for asylum or refugee status from those who arrive in Australia by boat. If Australia were to only accept applications from established refugee camps in places like Indonesia, the incentive for trying to reach Australia by boat would be greatly reduced.
Nothing much really. If you were living in a war-torn, poor country whith a despotic government and you saw Australians living in peace, in a fairly rich country, with basic social care (Medicare, just legal system, welfare payments etc) and a democratic government, wouldn't you want to migrate? Also, technically Australia can handle a lot more refugees than it currently takes. We receive less anually than England and we're at least six times as large meaning that we can take in more.