Here is exactly what I practice in grounding and centering; it’s pretty common, and involves breathing a taproot into the ground and using this energy cord to both draw in energy, and dissipate negative, or stale, energy. My centering is rather weird and idiosyncratic, however. Here’s the blow by blow:

For grounding, sitting and sending a tap root to the Earth’s core  is so similar to what I already do standing, that it was very easy to add the variation of sitting for the purposes of the first week, and of course, pushing the tap root down in rhythm to my breathing involved no changes. When I draw in energy, I tend to visualize the energy coming up as red, my colour for life-force, passion and vitality. I guess I don’t view it as ‘light’, so much as magma. It’s only after I draw it up through this energy cord that I view it as different colours of light, as needed. When purging energy, I gather it together first, until it looks like what an artist mixes grey in paint – all colours mish-mashed together, until it’s just ugly. Then, I push it out and allow it to burn up and be transformed at the Earth’s Core.

My weird method of centering comes from the fact that I took computer animation as a major in college, and in creating animated figures and setting them in motion, you have to create a centre of gravity for them. To do so is almost like creating a gyroscope – you have to attach it to the figure in its pelvic region and weight it correctly, or you get rather tragic results. 😉  I tend to envision an octahedron, stuck right in the centre of my body, just below my navel, as I tip my pelvis forward, tighten my abdominals and straighten my spine. Because of my spinal issues, my centre of gravity is below my navel. To set my balance, I visualise spinning this octahedron like a top, and using centrifugal force, moving this octahedron around until it ‘weights’ and ‘clicks’. I found I was still able to do this whilst sitting, so it was okay.