Collard greens have broad leaves with solid, firm veins running through them. They have a strong, vegetal flavor and a remarkably hearty texture. They don't break down easily, so they are good to use when you want a green that doesn't lose its shape and texture.
Traditionally, collard greens are cooked an exceptionally long time - at least an hour if not more - a process that fuses the flavors of the greens with cooking aromatics or liquids. If you don't want to cook them that long, you can try blanching them first and then sautéeing them like spinach or chopping them up and adding them to soups. You can also use them, once properly cooked, in dishes like Greens With Yogurt & Cumin.
Learn more about collard greens with this guide All About Collard Greens.