Harvesting Provence Lavendar

I have a beautiful plant of Provence Lavender in a fairly large pot that is full of purple flowers. I would like to dry some of the lavendar,, but have no idea how to harvest, when to harvest or what to harvest. The plant has stems with nothing but leaves, but others are a good 2 foot tall and full of both leaves and flowers, with the flowers being more profuse at the tips. When cutting the flowers stems, How far down the plant do I cut? I want to dry both leaves and flowers. Do I dry them on the stems, both flowers and leaves? Pardon my ignorance, this is the first year I've had any luck growing Lavendar and I have no clue how to dry it!