It depends on what the program does and how it impacts your clients.

You can look at www.ipaustralia.gov.au for basic information about copyright. However you'll need to speak with a lawyer who specifically works in the field of technology and ask them to prepare terms and conditions of use or an end user licence for you. That would be an agreement between yourself and your clients about the use of the program. You'll also need to consider appropriate insurance for your business as many off the shelf insurance products wouldn't necessarily be designed for technology businesses.

Good luck!

Unfortunately you don't give enough information for a good answer.

Are you trying to protect a program you've developed? Is it a computer program or a program you deliver in person? Are you expecting to be sued (and want to know how much you need to set aside to defend yourself)?

Best bet would be to speak to an IP Lawyer for 30 minutes to find out more about the possibilities are - perhaps ask for a review of your IP. Most will give you some time for free (in the hope you'll buy the solution from them).

I hope this helps.