Instructions
Browse through a course catalog at your community college to see if fashion design or clothing construction is offered. The instructor(s) may be able to tutor in hat making or offer recommendations. If your city has an art institute, they may offer hat making as a specialized course.
Check with the costume and wardrobe manager of your local community theater and other performance venues. These individuals are trained in fashion design and construction, and if you have the time and inclination, you may be able to work as an intern or volunteer. You'll pick up valuable skills while you learn hands-on.
Look up a local dressmaker (you can find recommendations from your dry cleaner, a wedding planner or via an online search) and ask about lessons.
Check etsy.com and eBay for artisans who make custom hats.
A school in Zurich, Switzerland, offers classes in hat making either on site or via correspondence, and a list of US hat makers, milliners and costumers who offer classes and supplies is available online (see resources).