Start with your usual trip
Think about a normal outing and list the items you already use. Keep a leash, cleanup supplies and other familiar essentials in a consistent place near the door.
Check before leaving
Review the bag before each trip rather than assuming it is ready. Refill used supplies and select any extra items appropriate for the destination and weather.
Reset when you return
Empty rubbish and return reusable items to their place. A short reset makes the next outing simpler and helps you notice supplies that need replacing.