First, don't
leave the
scene unless you like
hit-and-runs.
If
nobody is
injured severely and the
cars are still
drivable, just
exchange insurance information,
phone numbers, and
driver's license numbers, and
note any vehicle
damage. File a
police report even if there's
no damage, in case the
other person decides to
extort you later by
claiming nonexisting damage or
injury. If there is
serious injury or
damage, call for
help.