Traditionally, this pose incorporates leg movements as well, but focus on the arms only for tight shoulders.
In a comfortable seated posture, sit tall with hipbones evenly resting on the ground. Send right hand up and straighten your arm, then bend at your elbow.
Bring your right hand to the back of your neck, reaching toward the middle of the top of your back. With your left hand, grab your right elbow, and gently tug your elbow up and back for a tricep stretch.
For more sensation, bring your left hand behind your body to your low back, and reach up in the direction of your right hand. Your hands may touch for a bind, but if you have particularly tight shoulders, use a strap or towel in between hands to help assist.
Lengthen your spine by reaching the top of your head to the ceiling, and imagine your elbows are reaching away from each other.
Hold for 3-5 breaths, then switch sides.