Diagram 1 shows a typical scent-tracking pattern. The wider the track, the farther away the source. The stronger the wind, the narrower the scent trail, the weaker the wind, the wider the scent trail. Vegetation, rocks, and landforms in or near the scent trail can modify it, either spreading, narrowing, or diffusing it. Scent is carried by moisture in the air, so the greater the humidity, the stronger the scent.
Air temperature is next in importance, as warmer air holds more moisture.
When I pick up a new scent, I analyze it to determine its origin. Because we have a powerful scent memory, this skill advances rapidly with field experience. Extended rapid, short canine-style sniffs or repeated large inhales to test the air, dull our olfactory sensors. What works best for me is to catch the scent as I breathe normally. If I need to just keep connected with the scent trail, I take in just enough air to catch the scent.