A practical diaper bag is a small, flexible supply kit rather than a portable version of the whole nursery. For a short outing, consider diapers, wipes, a changing mat, a change of clothes, a bag for soiled items, and whatever feeding supplies your plans require. Adjust the number of items to the length of the trip, weather, and your baby's usual routine.
Use a few simple pouches to separate clean clothes, feeding items, and diaper supplies. Store medications or creams in their original packaging and follow their directions; keep them away from children. If you carry bottles, prepare and store them according to current food-safety guidance and your baby's feeding plan. A small cloth or burp cloth can serve several purposes, but avoid packing so much that the bag becomes difficult to lift.
Restock after you return home, replacing used diapers and clothes so the bag is ready next time. Check expiration dates on any products you keep inside and clean the bag periodically. If you travel by car, do not place loose items where they could become projectiles in a sudden stop. A bag that fits your stroller or can be carried comfortably is often more useful than one with many compartments. Let your real outings determine what stays in it.