I soak dry beans in salted water (as per Cook's Illustrated), drain, rinse, and cook in fresh water, usually in the pressure cooker. I used to discard the cooking liquid but recently have begun including it in soup. Depending on the type of bean, the liquid can be rather unattractive, so I add tomato paste to improve the color. Add beef or chicken stock or base (depending on color of liquid), aromatic vegetables, and improvise a vegetable soup with your choice of seasonings. Today I included lentils, mixed vegetables, chopped-up leftover pot roast, and some of the beans (pinto) back in at the end. The bean liquid will thicken the soup, supplying more body even if you don't actually include legumes in the finished soup.