This is difficult to see at first and takes practice. Keep at it though. It s worth learning. Pine needles are another difficult medium. Animals with hooves, such as deer, will break needles when they step in them.
Lighter animals don t tend to break the needles.
I ve noticed that, once pine needles have been stepped on, they bruise. Mostly though, you re looking for tiny breaks in the needles, and places where they have been scuffed up. Where I live, the forest duff is composed of redwood leaves. This surface is difficult enough to track in without counting in the fact that it rains so much here. In the case of redwood leaves, I look for places where the overall forest floor covering has been disturbed in some way.