I'm a Law student in Tasmanai, Australia, but I eventually want to be able to practice law in Australia, the United States and Great Britain. What qualifications apart from my degree would I require and are there any specialised rules that apply to me?

What area of law ? Limited in other nations ? More info needed?

In the US to practice law in a given state you must be admitted to the Bar in that state. Some states have reciprocity on this, but many do not. So in general what lawyers do if they want to work in a state where they have not passed the bar is partner with a local lawyer who has. If you are interested in international law you should be thinking about joining a firm that specializes in this - they will have offices around the world with accredited attorneys, and/or partnerships with local firms already established in the various jurisdictions.