What can I do to get lip swelling to go down?

Dependent on cause. Lip swelling can be a result of numerous causes. Trama, allergy to foods, irritation from exposure or contact to chemical(food additives, colorations, etc), and diseases. You need to seek help from dentist or dermatologist to determine cause and then treatment.
Ice it. The easy answer to swelling is always ice. However, you should find out the cause of the swelling. Trauma? Allergic reaction?