There is a good tourist information office in Quillan where you can find out anything you need to know about the local area. It is open weekdays throughout the year and weekends too in the summer. The building itself is unmissable — it used to be a Turkish baths and certainly stands out from the surrounding architecture.
There is also plenty of information, including downloadable pdf brochures and guides, on the official Aude tourist information office’s website: www.pyreneesaudoises.com