Of course it depends upon the walk.
For a five mile summer evening romp around a reservoir with MrsG. It's walking shoes on. Grab a drinks bottle and my camera and off you go. T shirt is usually fine.
For a walk in to Fur Tor alone mid winter.
Few days before.
Check the weather forecast.
Check my boots are dry and re wax.
Choose a start point and route.
Night before.
Check the Weather forecast.
Pack my small Rucksack.
Emergency box. Whistle, pain killers, plasters, pen Knife, foil bag loo roll.
Chock box. Selection of chocky bars that seldom get eaten, but I like to know they are there.
Lunch box. Usually make up a few cheese and Ham sandwiches.
Dry bag. Spare T shirt & socks, inner fleece, outer fleece.
Water proof Jacket , trousers & Gaiters.
Paper map. Compass
Seat mat. Brilliant things.
Charge my mobile & re check the Dartmoor OS map is loaded.
Charge my head torch, always carried.
Check batteries on my hand torch, only carry my hand torch if I expect it to be dark during the walk.
Fill my drinks bottles.
Check the car has petrol in it.
Morning of walk.
Check the weather forecast.
Make up a small flask of Tea.
Head off to the start point.
Discover all the previous weather reports were pointless, as the weather on Dartmoor has decided to do something different today. -14 wind chill last time I tried it.
Start walking.
Hope no one fell asleep reading that lot.