Don't buy too large of a quantity of dried herbs unless you will use them within one year, because they lose their potency over time. Spices lose potency too, although they are a little more robust.

Fresh herbs can be kept as a living plant in a pot on a windowsill, or in the garden in temperate climates. Fresh herbs, which can also be purchased at the grocery store, are best stored wrapped in a slightly damp paper towel and sealed in a plastic bag.

Some fresh herbs, such as cilantro and mint, are not worth using in dried form because their flavor is too delicate. Strong herbs, such as tarragon and oregano, can be used successfully in dried form and should be used sparingly in fresh form. They can be preserved in vinegar for winter use.

The form in which you should buy spices depends on the individual spice. Spices such as nutmeg and coriander are best if purchased whole and grated before each use rather than bought in powder form. Ground ginger and fresh ginger root have different personalities; the first is dry, and the second is wet.

The following is a list of herbs and spices in their preferred forms. Keep in mind that when substituting fresh herbs for dried, or vice versa, the quantity should change — use twice as much fresh as dried.