The pelvis is a boney structure that supports the spine. It's important to consider the way you tilt your pelvis because it will greatly impact how you will position the rest of your spine.
When seated on a chair or when bending forward, tilt your pelvis forward. This will not only encourage the base of the spine to move in the appropriate direction, but will also lengthen lower back and hamstring muscles.
When standing upright tilt your pelvis slightly back (to avoid sway back). If doing backward bends in yoga or any exercise movements, really tilt the pelvis back (top buttocks drawing to lower buttocks). This will lessen compression in lower spine.