1º_ To follow a trail, a footprint left by something or someone. It is used in a broad sense for "analyzing a series of clues until an unknown fact is discovered". 2º_ Buying or selling in a flea market. 3º_ Dragging or moving something very close to or on a surface, such as a fishing tackle on the riverbed or a rake on the ground.
To seek or follow the trail with a purpose. It means to follow, to pursue, to investigate, to find out, to ask. Follow the footprint or trail.