One of the biggest problems I faced in my classroom was missing marker covers. They would be on the floor constantly and kids were approaching me showing me a marker without a cap or a cap without a marker. I finally decided to make bins to sort these things into.
Students now know to put a cap into the cap bin and a marker without a cap into the marker bin. They frequently check these bins when they find either a cap or a marker missing the other piece. This has been a great way to solve this problem and save myself the cost of buying new markers.