How to pick the right perfume, every time

Anyone wandering through the perfume hall of an airport duty-free knows the problem. You feel overwhelmed and dazzled by choice, ready to brain the next attendant spritzing a celebrity-hyped brand.

What's missing, says Margaret Khoury, is the kind of logical order that bookshops and wine stores use. "You'd be confused if varieties were jumbled together, with shiraz next to riesling, or sci-fi next to biographies," she says. "It's common sense."