The basic kit
Check the lead and equipment attachment, then take waste bags and keys. Depending on weather and distance, add water, suitable clothing and a small towel after rain. Keep the list by the door rather than remembering it outside.
Before closing the door
Look at the dog: the garment is not twisted, the harness sits as expected and the lead is clipped. A comfortable walk begins in the hallway. A short outing needs little; a longer route deserves another glance at the plan.
Pack by what you need to reach
Keep waste bags and a small suitable reward where you can reach them with one hand. Put water and a bowl in a bag that is comfortable to carry while handling the lead. A phone is useful for contact, but should not occupy your hand during a tricky road crossing.
Check the identification tag and current contact information. Before a longer unfamiliar route, charge the phone and save the way back. A local walk does not need a huge backpack, but an empty bag roll is always discovered at the wrong moment.
On wet days, leave a towel at the entrance; for trips, pack a dry clothing replacement. Let each item solve a real problem rather than merely add weight.
Refill consumables when you return. Once a week, remove crumbs, check reward freshness and wash the bowl. A small ready kit is easier than rebuilding a checklist every time.
Useful? Save it for your next walk.