What should be done when a scab forms on a wound? Should I put polysporin on it? Should I put a bandage afterwards?

When a scab has formed on a wound, it is usually a sign that the wound is healing. It is generally not necessary to take any specific action, as the wound should heal on its own soon. You can leave the wound uncovered unless there is a risk of it getting caught on something. In that case, a simple bandage can protect it. As for using Polysporin, its effectiveness on minor wounds may be debated, but it could have been applied before the scab formed.