For using an Australian SIM-card for 15 days first of all your phone must be unlocked from its current provider. Is it? And your phone must be able to use the Australian frequencies and Australian 3G or 4G. Is it?
Then - with that hardware issues out of the way - you would need to find either a one month sim-only contract (if those exist) or a pre-paid sim-only service in Australia. The cheapest option, of course, depends on the number of calls, the number of SMS'es and the number of MB via 3G or 4G (not counting WiFi, of course) you expect to use in that 15 days. Without knowing that, nobody can tell what's best.
Incoming calls, by the way, are always free if you use a local sim-card.
Why not look at the site of a few Australian providers to see what they offer?
I have to visit Australia for about 15 days on a business trip to explore the new business markets and i am searching for some best deal or ideal cellular connection. Please advise me to decide which package, simcard or service should work best for incoming calls and internet usage during my stay.