I'd want to make sure it was a power cut first of all so I'd check the trip-switches.
I'd look out of the window for any signs the neighbourhood was out, or whether it was just us.
I did buy a load of battery-powered lamps a few years ago when power cuts were being threatened. If it was light when the power went off, I'd make sure I had the lamps handy and ready to go if the power wasn't back by nightfall.
I'd also dig out the power banks I own, so I could still use my mobile phone, and I'd switch it to silent and power-save mode to preserve what charge it had.
I'd dig out some handheld battery powered games consoles I have, for entertainment when it got too dark to read, and also my battery powered radio, assuming there would still be broadcasting.
I'd start thinking about what I could eat using only the hob to cook (if we still had gas) or, if no hob, what I could have to eat cold.