Slow, gentle cooking rather than boiling produces beans with a uniform texture and prevents skin breakage. Cooled in the cooking liquid, they remain moist and plump, with tight-fitting coats. If firmer beans with a dry texture and slightly more colorful skin are your preference (some like them this way in salads), boil the beans in unsalted water until just tender. Add salt to taste, then drain. For pronounced flavor, cook beans in broth with aromatics.