After a car accident, keep your nerve. The police always want to reconstruct the car accident. The information is many times based on what the other driver or drivers and you provide to the police. So the police will take statements from you and the other party. Remember to be sure on the information you provide. If you change your statement later it will of course affect your case.
First of all call the emergency services if there is an emergency situation. Always take care of injured people. Avoid as long as you can to move the cars in any direction before a witness have note the cars position. But if it will cause a traffic jam or massive traffic flow problem due to the car accident, then you have to move the cars.