If you're coming from the east coast of Australia the best way is with Air Austral from Sydney. They have 2 flights to Reunion per week on Saturdays and Tuesdays. You can then get either a connecting flight with Air Austral or Air Madagascar to Antanarivo (Capital of Madagascar) then another flight down to Tulear with Air Madagascar. The return flights from Reunion are every Sunday and Thursday. You should keep in mind that you will normally need to spend either a night in Reunion or Antanarivo before being able to get a connecting flight to Tulear. Same deal with the return flight you will normally need to spend a night in Tana before connecting back to Reunion for the Sydney flight. This does however depend on the period as Air Madagascar has direct flights from Tulear to Reunion during the holidays.