One of the things I have tried to do is to think of the things that are commonly misplaced, and make a permanent home for them. For example, I have a hook where I hang my keys. Sometimes, however, I am not perfect at hanging them there, so I have also trained the children to hang my keys there if they ever find them laying around. I worked really hard for a long time to get in the habit of hanging them in the same place every time, and now misplaced keys are rarely an issue. Another thing to do to help in this area is to go ahead and spend a little money to get an extra set of all your keys made- just in case. But on the “emergency” set, hang a LONG, brightly colored ribbon so that whoever uses them will not forget to replace them once theirs are located.
For security reasons, it is not a good idea to hang all your car keys right by your front door, but it is a good idea to have them someplace you walk past regularly- so be careful but practical when choosing your keys’ permanent home.