To brew an aromatic infusion, I like a simple method. Boil the water, just barely. Place herbs in a quart mason jar. Pour water over the herbs, cover immediately and tightly with the gasket and neck band, and let steep for 1-24 hours. Strain into another mason jar or other recycled glass jars (to carry). A French press works well too. For a strong infusion, use about an inch of herbs on the bottom of the mason jar. For a normal infusion, a tablespoon is standard.
Tommy Priester (who was taught this by Appalachian herbalist Phyllis Light) recommends boiling herbs for 20-30 minutes to extract the deep medicinal properties from the plants. This decoction method is especially useful when you don’t necessarily want to capture the aromatic properties of an herb – when using roots, stems, bark, berries, and many leaves – but you do want to extract the minerals and deeper nutritive qualities by breaking down the cell wall more fully. After boiling, strain and fully press the plant material out into the liquid, cool to warm, and drink, usually 3 cups 3 times a day. The amount of herb for this method is usually 1 tablespoon to a gallon of water, and the water boils down to about a quart and a half, or two days worth of tea.