White sage (Salvia apiana) has been used by healers for ceremonial and medicinal purposes for hundreds of years. It has the ability to clear negative energy when burned.
You can smudge yourself, others, a space (home, office, apartment) or any other healing tools you have like crystals. The main thing is to smudge with intention and mindfulness. Holding a piece of sage, light the end with a match or lighter and let it burn well for a few seconds. You want the sage to burn slowly. Once you have a steady stream of smoke, gently wave your arm to allow the smoke to envelop you.
Other options are to fan the smoke with a feather or place the burning sage in a small fireproof dish on the floor and stand over it.
To clear a space go to each corner of every room and allow the smoke to trail up to the corner for a few seconds. Start with the room furthest from the front door to help the energy flow out. In each room follow that same logic of starting with the corner farthest away from the door. Repeat in each room as necessary. Feel into the energy of each room and notice when it changes. Some places will need more than one round of smudging.