Upon first whiff, one might not be inclined to cook with epazote, as it has a pungent, petroleum-like odor. (The word epazote comes from a Nahuatl term meaning "skunk sweat"!) Eaten straight, the leaves can taste like a curious combination of turpentine, mint, citrus, pine, oregano, anise, and mustard greens.
For some this may fall into the "acquired taste" category, but we find that epazote really mellows out during cooking and can add a wonderful dimension to dishes like black beans, corn, and even cheese quesadillas. We generally use about 1-2 tablespoons of chopped fresh leaves (younger leaves are better) or 1 teaspoon of dried leaves in a pound of beans. (Be aware that too much epazote can overpower a dish and even lead to nausea.)
Here in Southern California we forage for epazote, which grows wild, but it may also be found fresh or dried in Mexican, Central American, and Caribbean markets, at farmers' markets, and from spice merchants. Fresh stems should stored upright in a glass of water or in the refrigerator, wrapped in a damp towel and placed in a plastic bag.