Bring the temperature of the plant slowly up above freezing. Some people recommend shading a plant from sunlight to keep the temperature from rising too quickly and causing further damage to the plant's tissues.
Water the plant slowly and deeply once the plant's temperature rises above freezing and give the plant liquid fertilizer to help speed up its recovery. Do not over water the plant, as this could cause more damage.
Remove any damaged leaves, stems and flowers from soft-stemmed plants to prevent rot. Do not trim shrubs, trees or plants with woody stems until all risk of frost has passed because the damaged plant material will protect the plant if another frost occurs.