I find packing for shorter trips harder, than longer ones.
DH despairs of me sometimes, but, when he finds he's forgotten something, or the SC place doesn't have what we need he remembers my over preparing is actually a godsend!
I have admittedly got better though.
Clothes that will do for either hot, cold or wet weather. I just layer as appropriate.
Walking boots and trainers are mandatory. I then take one pair of flat black pumps and one pair of black flip flops as they will go with all outfits. Lightweight waterproof coat, with additional pac a Mac and large umbrella.
I use packing cubes for clothes. Keeps everything neatly organised and a fabric laundry bag for mucky clothes, so they are kept separate at all times. I always pack extra underwear and socks.
I always pack blankets. The car permantly has 2 in it.
I take kitchen utensils: decent sharp knives, a grater, corkscrew/bottle opener and decent wine glasses. In addition I pack kitchen roll, rubber gloves, tea towels, foil, cling film and decant washing up liquid.
I hate paying for things I need when I know I have the stuff at home, especially when it's usually overpriced.
I also, always take my own booze. Nothing worse than finding out your destination doesn't stick your favourite wine/rum!