In earlier times, throughout the world, people built mounds or piles of stones. These were sometimes formed to mark the passage of travelers, or to commemorate some historic even, but such cairns usually had ritual significance.
In magickal thought, cairns are places of power. They concentrate the energies of the stones used to create them. Cairns are rooted in the Earth but lift upward to the sky, symbolically representing the interconnectedness of the physical and spiritual realms.
During outdoor circles, a small cairn, composed of no more than nine or eleven rocks, can be fashioned as each point of the Circle of Stones. This can be done prior to creating the circle itself.
The next time you're in some wild, lonely place with a profusion of stones, clear a place among them and sit. Visualize a magickal need. As you visualize, grasp a near-by stone. Feel the energy beating within it - the power of the Earth, the power of nature. Place it on the cleared ground. Pick up another stone, still visualizing you need, and set it next to the first.
Still visualizing, continue to add stones, building them into a small pile. Keep adding stones until you feel them vibrating and pulsating before you. Place the last rock on top of the cairn with firm ritual intent - affirm to yourself, to the cairn and the Earth that with this final magickal act you're manifesting your need.
Place your hands on either side of the pile. Give it your energy through your visualization. Nurse it. Feed it strength and see your need as being fulfilled.
Then leave the cairn alone to do its work.