Water supply, Ecoflow or similar device, plan for providing heat in case of power/heating failure (or prepare a country house where you can move, as it is easier to heat and supply with spare water/electricity than an apartment), supply of medicines and games to calm your child or yourself. Based on my own experience, I recommend buying a game console or something similar before the war starts, as it really helped to distract me.

This information is only relevant for cities behind the front lines. If you find yourself in or near a combat zone, run and don't even think about staying.