To get the best advice, alleviate you form stress and make your visa application less complex.
Some visas could look easy and straight forward but with the ever changing legislation you have to be very careful you get it correct the first time as once refused it becomes harder to change and could jeopardize your chance of residency in Australia.
Similar to using any other professional to make sure that you get the correct advise and that you get the best result you are after (for example a tax accountant to do your tax returns, or solicitor to write up your will). Getting your immigration work done professionally is your best chance to success.