Grab the edge of the bench or whatever you are sitting on and then tilt your head in the opposite direction. Meet your ear to your shoulder. You should feel this stretch down into your arms, and sometimes even down into your fingertips.
Bring our forearm out in front of us, clasp the top of our palm, and bring that arm down so that our fingers are facing into our body. Be sure to completely lock out this elbow. Reverse it to where your fingers are facing inward and repeat the stretch.