Most garden herbs are at peak flavor in summer when heat and flowering maximizes oil content in the leaves. This is the best time to harvest and dry fresh herbs for future use.
Cut herbs in the morning after the dew has dried. Harvest long stems, but make sure to leave some foliage on the plant to nourish it. If the herbs are dirty, gently rinse them off and spread them out on a tray or screen to dry. Tie the herbs in bunches, securing the stem ends with string. Hang bunches upside down in a warm, dry place out of direct sunlight. If the drying area is dusty, place a paper bag around each bunch.
If you want to harvest seeds of herbs like dill or coriander, place a paper bag over the seed head just as the first seeds are dropping. Cut the stalks and hang them upside down. The seeds will fall into the bag as they dry.
Most herbs will thoroughly dry in about two weeks (they should be nice and crunchy). To preserve, strip the leaves from the stems and store them in labeled, airtight jars. Place the jars in a dark cupboard.