Some call it New Age or VooDoo, but smudging is actually a common practice in Native American tradition and even some religions.
The use of burning aromatic herbs such as those in a smudge stick or incense plays a role in spiritual, emotional and mental clearing/purification. It is common to smudge a new office space or living space or during a general spring or fall housecleaning. Basically, smudging is a ceremonial way to clear out negative energy or influences that might promote bad feelings. Smudging can also be a part of a Blessing Way for an expectant mother.
The elements used in a smudge stick or for smudging include the herbs White Sage, Cedar, Sweetgrass, Pinon, or Lavender. A combination of these elements are gathered and tied in a stick-like bundle and allowed to dry thoroughly. You can also purchase premade smudge sticks from online vendors such as www.taosherb.com , www.madeinnewmexico.com or even Amazon. Many kits are available that have a receptacle to use while burning, either terra cotta or an abalone shell. Add sand to the receptacle to put out the lit smudge stick when finished.
Light the smudge stick with a candle or other long burning flame source. It often takes a few minutes to thoroughly light the stick. You do not have to use the entire smudge stick at one burning. Having too much of the burning herb smoke may cause respiratory problems in infants/young children, pregnant women or the elderly. And as with other flame sources, never leave a smudge stick unattended!
You can read more about Native American smudging rituals at http://www.asunam.com/smudge_ceremony.html or http://www.nativeamericanresearch.org/smudging.html