Tip # 2. If you do call 9-1-1, even by mistake, do not hang up the phone.

9-1-1 call takers are trained to get the most important information as quickly as possible to get help on the way to an emergency situation.  In an emergency situation, allow the call taker to ask you all the questions they need in order to get help there in the timeliest manner before you hang up or leave the phone.
If you happen to call by accident, stay on the line until you can tell the call taker that you called by accident and there is no emergency.  This saves the call taker from having to call you back and confirm there is no emergency or sending police with lights and sirens to check your address for an emergency.