when calling 911 it is good to know what equipment you need on the scene, for example, the dispatcher will ask if you need police, ambulance, or fire.
if you were in a car accident all equipment will usually show up to make sure all patients are taken care of.
for example, if your house is on fire or got into a car accident you should definitely call for help
instances when you should call 911 is when you are in serious trouble
although dispatchers are trained for most situations, sometimes the 911 call is unnecessary. an example would be if you fell off your skateboard and scraped your elbows.
when on the phone with 911 keep yourself calm and collected the person on the other side of the line will talk you through the situation and anything you can do in the moment by yourself until help comes.