Take frequent breaks while quilting, and do some backwards bending. We don't bend our spines enough in that direction. Get one of those big exercise balls, and lay back on it and roll backwards to stretch your spine over it, in that backwards curve. Sounds strange but it really helps! To stretch out the shoulder area, reach your arms overhead while bending backwards over the ball.
(You can also keep your abs in shape with one of those balls in the house!)
Forgot to mention Ibuprophen and ICE: the two best things to reduce inflamation, and therefore, pain.