How do you dilute aromatherapy oils such as lavender oil?

The typically recommended method is to use one to two tablespoons of a base oil, such as Jojoba, Apricot Kernel, Grapeseed, etc., and add as many drops of the lavender as you need.

Lavender is considered a "middle note" in aromatherapy, so you can use anywhere from a few drops up to 10 or 15, depending on your needs.

Do a little more research, as the amounts to be used for environmental (smell-good) aromatherapy differ from the amounts used topically (on the skin), esp. on babies and expectant mothers.