In a diffuser
Follow your diffuser's own instructions first. As a guideline, 3 to 5 drops for every 100 mL of water in the tank. Run it for 30 to 60 minutes, then rest it for as long. It mixes well with lavender here, and is used to freshen a bathroom, or a kitchen after cooking.
The 3 to 5 drops are a guideline from the Tisserand Institute's support team; the timing is from the Tisserand Institute's safety guidelines.