By finding the center of the rock, the line of gravity straight through to the earth's core, I center myself.
There are few activities that shut off my mind; allow me to stop the train of thoughts and just breathe in the here, the now.
Choose the rock; or perhaps let the rock choose you.
Pick it up, feel it.
Breathe, relax, close your eyes... then choose a side and set the rock in place.
Sometimes it just stands right there. Other times you have to hold it, coax it, feel its movements.
Here are some of my favorites: