Steps to take during freezing temps:
Be sure to fill your pool to the correct water level before freezing temps hit if possible
Make sure all the skimmer and pump baskets are clean and kept clean so water flow is not restricted.
Make sure the main pump is running properly and operating during the freeze. If you have an automation system with freeze guard protection, it should override your scheduling and keep the pump on until temps get above freezing again.
Any other pump (excluding the automatic cleaner booster pump) must also be operating or properly winterized before the freeze.
Backwashing or cleaning your pool filters before temps drop is also good practice
It is okay if the surface of the pool is frozen! Just make sure the water is still able to flow freely into the skimmer openings. Check the Wier!
You do not need to run your pool heater if your pump is properly moving water through the system.
Store a garden hose in your garage in case you need to add water later.
If your pool equipment (pump & filter) sits above the water level in your pool, it is safe to pull the plugs. DO NOT pull the plugs if the equipment is below the waterline, the pool could then gravity drain out through your equipment.
IF YOU LOSE POWER TO YOUR POOL
The only thing you can do at this point is to remove the drain plugs on your pumps, filter, and heater(again, only if your equipment sits above the level of your pool water!) in hopes of minimizing damage to your equipment. If you take this step you will need to also turn off the breaker to your pool system to prevent the pool from attempting to operate without water.