If no injuries have occurred then call the local police.
When the police come they will ask you and the driver of the other vehicle a lot of questions about the accident. They will take down all your information (drivers license, insurance information, what directions were you moving, and other pertinent information so as to establish the conditions leading up to the accident. Answer as truthfully as you can based on your memory of events.
Who is responsible for calling the tow service?
Here's a scenario -
It's Friday afternoon and Joe is driving near his residence and is involved in a collision with another vehicle. No one is injured but Joe's car has damage to the front tire and the car will not be able to be driven from the scene.
Now Joe has an old college friend, Bill who owns a body shop close by with a towing service and he knows and trusts his friend to be fair with the towing expense and to fix his car. However, in heat of the moment Joe forgets about his friend's towing business and doesn't mention that to the police officer attending the scene. The police have a responsibility to clear the intersection and make it safe for traffic. The city police have a contract with another towing company and make the call to them and Joe's car is towed to their lot.
The city towing company tow Joe's car and it is put in their lot. Joe's wife picks him up and they both go home. After awhile and the shock of the accident has subsided Joe calls the tow company to make arrangement to get his car over to his friends body shop. This is no answer. Joe and his wife drive to the impound lot to find them closed. Joe's watch says 5:30pm. Joe looks for any sign someone is there but finds nothing. The tow company is closed both Saturday and Sunday.
Joe calls on Monday morning and gets his car towed by his friend to his body shop. Now Joe gets his towing bill and the towing fee is $200, labor is $150, administrative fee is $125 and storage is $100 a day for 3 days. Joe's total bill is $775 plus he's going to have to pay for another tow. Had his friend provide the tow Joe's total bill would have been $175 for the tow. It's going to cost Joe $600 more than it should have. What to do?
1) Joe should have told the police to call his friend Bill for the tow direct to Bill's body shop.
(If Bill's towing was prompt and quickly arrived at the scene Joe would have saved a lot of money. But if the police determine that Bill isn't responding quickly enough and call the city tow service then whoever shows up first and hooks up to the car is entitle to the tow)
2) Joe contacted the city tow service owner and showed him his phone bill documenting his phone call on Friday prior to their closing hours. The tow company didn't have a phone number posted for after hour calling and since the tow company owner wasn't aware that Joe had called prior to closing he agreed to return to Joe the cost of the 3 days storage.