On a fundamental level, there are four elements: Earth, Fire, Air, and Water. Each element has associated methods for destroying or releasing the sigil according to its elemental association.
The Earth represents physical matter. Therefore, keeping your sigil visible or burying it in the ground allows it to be transmuted by the element of Earth.
Air symbolizes the mind or space. Thus, by inscribing the sigil on a piece of incense, or cutting it into small pieces and casting it into the wind, it is transmuted into the Air element.
Water symbolizes time and emotions. Given that humans are approximately 70% water, dissolving the sigil in water allows us to transmute our spell into the water element.
Fire represents energy, an element closely related to spirit or chi. It can also be thought of as electricity. By burning the sigil in fire, we transform it into energy. This energy then disperses into the world and reconstitutes as our desire.
Wood, in many cultures, is associated with life, growth, and renewal. It can be viewed as a bridge between the earth and the air, taking nutrients from the ground and releasing oxygen into the atmosphere. As such, carving a sigil into wood or allowing it to decompose naturally could symbolize the transformation and growth processes inherent in the element of wood.