A leading line can be almost anything: a road, path, sidewalk, fence, river, hedge, tree line or shadow. You will not find a strong leading line around every subject, but you should look for them if they are there and take advantage of them. Lines in a picture should lead into, not out of, the picture, and they should lead your eye toward the main subject.
Sometimes it is a matter of choosing the right angle or point of view to make leading lines lead into the picture. Starting a leading line from the corner of your picture will often improve composition.
Remember: Watch for strong lines that lead to your subject.
