When packing for a trip, "pack by numbers."
In her hack submission, Katherine said her tip was "perhaps blindingly obvious, but still made her happy." Once again, what's obvious to one parent makes another smack her forehead at the brilliant simplicity. *smacks forehead*
When packing for excursions, it's easier to keep track of toys and baby accessories if you pack by numbers. In other words, take the same number of similar items (cars, crayons, soft toys, pacifiers...) so you can easily do a mental inventory when it's time to leave: "Have I got three cars? Check. Three crayons? Check. Three food-related things (bowl-spoon-snack)? Check." (..."three kids.... Ack! Where's the little one gone?")
Having a set number to look for can also make it easier to involve small people in remembering/finding their toys: you can ask them which car is missing, or to help count up all the things in the bag before you leave Grandma's house or get off the plane.