For some great information on lavender see Gracious Hospitality at http://www.gracioushospitality.com/ I recently moved my lavender plant from the front to the back yard so I won't be getting much this year! Next year though!
Nothing is easier to grow than mint! You will find you have to pull it out so that it doesn't take over everything! You can freeze mint in ice cube trays with water for some lovely ice cubes for your ice tea!
To harvest your herbs you may need a food dehydrator in very humid climates. When I lived in Virginia I dried herbs in my oven at 100-125 degrees for 2 hours. The smell is delightful. Here in Colorado we can simply wash them with the water hose and bunch them, rubberband and hang them up to dry. If you are going to use them later they need to be put in plastic cartons after they are dry and kept out of light. You can also freeze them in ziplock bags.