Harvest leafy herbs at the peak of flavor, right before they begin to flower. Often this happens in midsummer. Clip the plants in the morning, after the dew dries but before the day gets hot.
Snip bunches or sprigs with pruning shears, or pinch the top 6 inches of the plant off the stem.
Rinse the cuttings gently in cool water to remove any dirt, debris, insects or other matter. Shake them lightly to remove excess water.
Lay the window screen flat on a counter and position a layer of cheesecloth over it. Pick the foliage off the stems; spread the leaves to dry on the cheesecloth.
Place the screen in a warm, dry area without exposure to drafts or direct sunlight. Leave the screen undisturbed until the leaves fully dry and become brittle, typically several days.
Store the dried herbs in airtight containers, such as small glass jars. Check the jars two days after you fill them to make sure they remain dry inside. If the jar or contents seem moist, spread the leaves on an oven-safe tray and dry them for a few minutes in the oven, with the door open, at lower than 150 degrees F.