Switch off your electrical appliances – so they don't get damaged from the power surge that happens when your electricity comes back on
Leave a light on – so you know when your electricity comes back on
Check your neighbours – if their electricity is out too, your local area has power cut (if they have electricity, you might want to check your trip switches)
Call 105 to report the power cut – this number gets you through to your local electricity network operator (calls are free)