Supernatural - main recommendation was to confess your sins, ask God for forgiveness through prayer. If they got the disease, was Gods will, if it was his will the patient would die, no cure that would work.
Natural - to begin with physicians tried bleeding and purging, done for the Four Humours, didn't work, seemed to make people die more quickly. Then recommended strong smelling herbs, believed to have cleansing properties, lighting a fire and boiling vinegar also prevented miasma. Physicians or surgeons sometimes lanced the buboes - occasionally, people whose buboes burst survived.