The gravitational pull of the moon can affect how plants grow, pulling the sap to and from the roots, and causing water in the earth to either sink down or rise to the surface. This is how farmers knew when to plant and harvest, and you can use this same effect to get the most out of your herbs.
During the moon's waxing phase, water in the earth is drawn up to the surface, making it a good time to plant any vegetables, herbs and flowers that bear their fruit above ground. During the waning period when water is pushed down and inwards, the time is right to plant bulbs and root vegetables.
When harvesting, remember the waxing period is prime time for harvesting the above ground parts of plants (leaves, flowers, etc) and the waning period is for gathering roots and bulbs. This is because at low tide, all the nutrients and chemical constitutes of a plant are pushed upward, and at high tide when the oceans are pushed down, so is the sap of the plant.
Herbs should be harvested in the early morning, after the dew has dried but before it becomes hot, when the sun causes the oils of the plants to evaporate.
When the moon is waning and the plant nutrients are draw inwards, take down and store dried herbs.
Start your herbal oils and tinctures during the dark moon, and let brew for 1 (or more) full moon phase, which is two weeks. This waxing period helps fully draw out the nutrients of the herbs. Then when the waxing period reaches its strongest peak at the moon's fullest, strain and bottle your formulas.