Smudging is an ancient practice or ritual where you burn dried sage or other dried herbs to cleanse a person or area. With sage, sandalwood, mugwort, or other dried herbs in hand, simply light a small corner of the herb and blow it out. It is best to have it in a holder of some kind so that the ash stays intact.
Go around the area that needs cleansing and let the smoke get to every corner of the room. It is always wise to have a window open while smudging so that the negative energy has somewhere to escape.