Sage smoke is proven to purify the air of impurities and bacteria, as well as negative energies. This ancient herb has been used for ages in the occult and metaphysical communities for ceremonies, rituals, and as a natural cleansing aid. It is recommended to burn the sage stick before and after rituals to make sure your area stays pure of any unwanted energies. 
 
How to use: 
Hold sage stick at one end, with the other end away from you. 
Use a lighter or match to burn the far end slightly until the leaves start to smoke. Blow out any flames. The goal is to smolder the sage, not quickly burn it like tinder. 
Walk around the area you wish to cleanse while holding the stick. Or you can place it in a smudge bowl and allow the smoke to drift naturally. 
Be sure to hold the intent of cleansing the area when burning the sage!