It is preferable to actually measure a pair of the subjects shoes rather than trying to establish a length from a shoe size because lengths for a size often vary between manufacturers and models. Disturbances left by a subject's passage through an area include discarded material, footprint fragments, broken and bruised vegetation, grains of sand on the underside of leaves and grass blades, dislodged or crushed stones or dirt chunks, dirt prints on an asphalt road, or a flattening of a surface area. The characteristics of these disturbances will change with time and are also effected by weather, terrain, time of day, and the passage of other people and animals through the area. A good tracker does not have a preconceived notion of what form a clue will take. It is important to be patient and look at everything.
Clues are generally parts of the whole, for example, a partial arc of a boot heel or a broken twig.
Different environments will show clues in different ways. When examining a material for clues, think about how a person would leave a clue in the material, as opposed to clues left in the material by an animal or occurring through some other natural means. The flatting will often appear as shine, reflecting light differently than the natural material. Shine frequently is easiest to see looking towards the light source at a distance from the area of shine and with the light source at a low angle. Shine will often be noticed on flat, hard ground that otherwise does not reveal clues.