To not admit fault. Insurance companies know they are in a better position if their insured does not admit fault.
When fault is in doubt at the scene of an accident the cop will interview the drivers and see if someone will admit it was their fault then they will get the ticket. If no one admits fault, no one gets a ticket. Unless there is other evidence of course.
Same goes for if a person is stopped for speeding. The cop will often say something like, "You were going 95 in a 75 mile per hour zone." So you say "I think I was only going 85." So the cop gives you a ticket for going 85 in a 75 mile per hour zone and you can't contest it because you admitted it. Tricky.
So never admit fault or you will get the ticket.