Since it grows in slightly cooler temperatures, chard is often seen on fall tables.
Chard is well-known in Europe and in fact was "one of the earliest cultivated vegetables ("The Secrets of the Seed Vegetables, Fruits and Nuts" p21).
According to Larousse Gastronomique, it is best to serve chard with its own cooking juices, or served with a thin white sauce (p248).
Chard has a somewhat earthy taste, like beets. Sautéed chard, for instance, can be a simple side dish on its own or it can be included in vegetables stews such as stewed lentils, or in soups. Chard is commonly added to soups in European cooking.
Chard goes well with alliums like onion and garlic. Simply sautéed with garlic and olive oil is a timeless classic. Maybe even top it with some parmesan cheese or a seasoned bread crumb!
To find inspiration, think how are other dark leafy green used in cooking? Dips, stews, pastas...