Allison Tan never thought of herself as a stalker. Yet there she was on a recent Saturday, following a man to his car. Her goal: his prime parking spot.

'He was really nice about it,' says Ms. Tan, who was shopping with her boyfriend at Garden State Plaza in Paramus, N.J. 'He waved me over. It was only through the goodness of his heart that we found a parking space.'

Circling around a parking lot hunting for a space is one of most irritating experiences, especially this time of year. Truth is, though, there are usually available spots