You, driver, car. In that order all the time. Just to stay with some fundamentals, because this kinda thing will send you right off the rational logic scale in a hurry if you don't remember the basics to start with. YOU have to get there safely to be of any help to the DRIVER to help sort out the issues with the CAR.
NFPA 610 has some good 'guideline' information.
It's important to have a good working relationship with your ambulance crew(s). Remember why they are there, and reacting to their directives as the professionals in that situation. Or any injury situation. They need to know who the Incident Commander is. That would be the individual that is not just a voice on the end of a radio, but the person there, physically and charged with coordinating efforts on the ground at the incident.
You hear about the "hand-off". Well, it's not very complicated. Once the ambulance is on scene, Safety provides them any information, and assistance necessary to tend to our driver, their patient, and get them on their way to wherever they need to go. Not much different than a Turn Marshall waving at us, and saying, "Thanks for cleaning up that mess they made."
That means closely coordinated, and discretely guarded communications with Base Comm, or other, so that they may keep the Stewards, and Race Chairman, and others informed to provide coordination with those individual responsibilities, like hot pit, grid, and track traffic, (FCY w/Pace, or other EV's on course) to accomodate emergency egress of the ambulance, arrival of Life Flight, and estimated times.
Where is Life Flight going to land? Who's in communication with the bird?
How do you secure the scene (covering the car is more for prying eyes, and 'unofficial' cameras than anything)?
Who gets to take pictures? Who is responsible to take 'official' pictures?
Will the Race Chair(s)/Steward(s) want to inspect before it's cleaned up, or before the car is moved to impound?
When the Race Chair, or Steward arrives, is the Incident Command transferred? That's another 'hand-off' situation. One that should be considered before 'hand' to avoid confusion. It's important for the rest of the crew(s) to know who's has local authority for the 'zone'.
Robby knows I can't resist this stuff.