Please, refer to the official roads authority in your state/territory. For NSW, the following is the relevant link.

http://www.rms.nsw.gov.au/geared/your_driving_skills/car_crashes/what_to_do_in_a_crash.html

In brief, if nobody is hurt and all involved vehicles can be driven safely, take photos of the following.

1. Other drivers' licence(s)
2. Plate number(s)
3. As many photos of the involved vehicles as necessary 
4. Details about insurance companies for the other vehicles
5. NO need to call the police

If someone is hurt, or any of the vehicles cannot be driven, you need to do the above and call the police (and the ambulance - if necessary) on 000.

However, please make sure you refer to the roads authority in your state/territory and make sure you read the details very carefully. 

For more information about the procedures for car accidents in NSW:

https://www.police.nsw.gov.au/safety_and_prevention/crime_prevention/road_safety/crash_reporting_faqs

بالنسبة لتحديد الشخص المخطئ، فيكون ذلك بالحوار بين الأشحاص الذين تم بينهم الحادث. بفرض أن الحادث كان بين سيارتين، يكون هناك على الأقل طرفان (هما مالكا السيارتين). وعليهما أن يتفاوضا "بشكل ما" لتحديد الطرف المخطئ أو نسبة الخطأ على كل طرف.  

أما لو كان أحدهما أو كلاهما لديه تأمين، فإن شركة التأمين تدخل كطرف إضافي في المفاوضات. وشركة النأمين لها مصلحة بأن لا يكون عميلها مخطئا لكي لا تدفع مصاريف الإصلاح. وعادة يتم كل شيء عن طريق مكالمات تليفونية!!!

وعلى أي حال، فمن الهام جدا أن تقوم بتصوير السيارتين ومكان الحادث، ليكون ذلك توثيق لما حدث.

ولمزيد من المعلومات عن الإجراءات المتبعة في ولاية NSW: 

https://www.police.nsw.gov.au/safety_and_prevention/crime_prevention/road_safety/crash_reporting_faqs

In Western Australia according to WA police

The driver of a vehicle must report a traffic crash when the incident occurred on a road or any place commonly used by the public, e.g. carparks; and

• the incident resulted in bodily harm to any person; or
• the total value of property damaged to all involved parties exceeds $3000; or
• the owner or representative of any damaged property is not present. 

You will need to provide the following information:

• date of crash
• time of crash
• precise location of crash
• your personal details (taken from your driver's licence)
• your driver's licence number and expiry details
• your vehicle licence plate and expiry details
• details of other involved drivers/passengers/owners/vehicles/witnesses 
• details of your injuries and other person's injuries
• crash features (traffic control, road features, road alignment, other conditions)
• total estimated cost of damage to all vehicles and property
• description of how the crash happened
• optional - digital images of the crash incident. Up to three images may be loaded into the online report. Each image no larger than one megabyte (1Mb) in size.