An important fact to keep in mind when buying perfume is that fragrances evolve over time. "When you first spray it's going to be totally different then the way it smells an hour from then," says Hockstein. "Most perfumes are built that way, so you can't go with your very first impression. Wear it for a couple hours." Sometimes she even tells customers to go home with a sample so they can see how the scent holds up over a longer period of time.