Heater motor wont work

My heater motor wont work!
Worked fine when I parked it and when I started it, the heater blower motor wont turn on...
Any ideas on where to start my troubleshooting?
Thanks in advance!

If this is on a 1980 (B-Body) Impala, jumper power directly to the blower motor and ground the blower ground tab directly to see if it runs. If so, you can eliminate the motor and start looking at the high speed relay, blower resistor, and blower switch. Make sure the HEATER fuse is intact.