Membership of the Qantas club gives you lounges acces rights to all Qantas Clubs, British Airways Executive Club (or business class) lounges and all AAmerican Airlines Admirals Clubs provided your next onward flight is on one of those airlines.

So if you are flying ex JFK on BA then you are welcome to use their lounges in JFK. Any domestic flights you have in the USA, if they are on American Airlines, will give you access to Admirals Clubs (where available). Any flights out of the UK on BA, or within Europe on BA will also give you lounge access in cities where BA has a lounge (although I seem to remeber there was one exception at somewhere like Paris, but I'm not sure if that still applies?).

If you are departing on a Qantas flight then you have access to the Qantas Club in that port, OR to the business class lounge used by Qantas at that port. (So for example, if you are flying on a QF aircraft ex India or China they don't have their own lounge, but you can still use whichever lounge they use for their business class passengers.)

The exceptions for QF club is if you are travelling on a codeshare operated by another airline such as Jet Airways from India to Singapore. Even if you are on the QF flight number you DON'T get lounge access.

In Australia and Asia your club membership also gets access when flying Jetstar (in ports where there is a Qantas Club, so that's singapore, hong kong and bangkok in addition to all main Australian cities).