One of the marks of a truly great gourmet cook is knowing how to use herbs well. Herbs can enhance almost every dish we create, but most people just don't use them properly.
Dried herbs are readily available on almost any grocer's shelves. Like most gourmet cooks, I keep a complete stock of dried herbs in my cupboard. In fact, I often dry my own. There's nothing wrong with using dried herbs when fresh aren't available and they can be a real boon to a cook who's in a hurry.
However, drying greatly diminishes the potency of herbs. And, although the flavor will be similiar, dried herbs just can't compare to fresh.
When buying fresh herbs at the grocer, remove them from the plastic bag or other container they came in as soon as you arrive home. If you don't, they'll wilt and deteriorate very quickly - in as little as one day or less.
You can greatly extend the life of fresh herbs by standing them in a bowl of water and covering them very loosely with plastic. Be aware that you'll have to change the water every few days, though. By doing this, you can keep fresh herbs in your refrigerator for up to a week before having to discard the unused portions.
An alternative is to wet a few inches of a paper towel and wrap it loosely around your bunch of herbs, then store them in a plastic baggie in your refrigerator's vegetable drawer.
Of course, the best way to obtain the very freshest herbs is to cut them from your own garden right before use. Herb gardens don't take up much room and don't require a lot of care and the luxury and joy of being able to step outside and snip a bunch of rosemary, thyme, parsley, basil, or dill anytime you need it is certainly worth the time you spend caring for the garden. If you live in an apartment and just don't have any space available outside, consider growing the herbs you use most frequently in pots. You can purchase them as seeds or seedlings at any good nursery. Not only will they enhance your cooking, they'll enhance your kitchen as well with their cheery, inviting look.
Using herbs correctly, and using fresh herbs whenever possible, is one of the things that separates a gourmet cook from a cook who's simply adequate.