This stretch is great for releasing tension in upper arms and shoulders. You can even do this sitting down!
The most important thing is to keep both shoulders, especially the shoulder of the arm you are stretching, rolled down and back. As one of the great Barre & Soul teachers, Whitney, likes to say - "Shoulders don't make good earrings!"
To do the stretch, reach one arm straight in front of you, then bring it across your chest. Hook your other arm across it over the upper arm and pull across your chest. To deepen the stretch and add a stretch for your neck, turn your head away from your arm (towards the side of the shoulder you are stretching). Then repeat on the other side!!
(do I have a pic of eagle arms I can add for next step?)