Earthbending is possible by controlling energy (chi) that flows through the meridians of the body.
Earthbending is a very difficult skill to learn and takes a LOT of time and patience. This is why there tend to be fewer earthbenders than any of the other elements. Good luck. Here are some techs to get you going:
Beginner's Lift: First, find a quiet spot where you'll be undisturbed for a while. Sit in the Lotus position, cross-legged if you can't bend that way :P Find a small stone, and place it in front of where you're sitting. Put one or both hands on the stone, and close your eyes. Repeat the meditation breathing until you enter the state of blackness, and visualise a white, moon-like substance: your Chi, flowing all through you in streams. Focus on your abdomen, under your belly button. See a pool of Chi there, and visualise it flowing up, splitting into two streams when it reaches your chest, and flowing through your arms, into your hands, past your fingers, and into the stone. See the stone start to glow white as it fills with Chi. Once it's fully glowing, stop feeding it with Chi and visualise small thread-like strings connecting your fingertips to the rock and the Chi inside it. Then, slowly raise your physical hands, and visualise the strings pulling the stone off the ground as you move your hands up. Stop raising your hands and hold them there about three inches off the ground. Don't expect much on the first or even second try, but if you do it right, when you open your eyes the stone should have risen with your hands. Keep trying even if it doesn't work. You will get the hang of it eventually.
Page under construction, more techs on the way.