These active stretches are the brainchild of my friend Colin.  They are excellent!

1) tuck chin hard and pull shoulder blades back together, really stretch the pec minor and hold for 20secs

2) tuck chin, pull shoulders down and internally rotates arms as hard as you can and hold for 20secs. Arms will be locked straight

3) the same but externally rotate them, with arms coming out to the side away from the body. It will naturally go there anyway and pulls arms towards the rear a bit, locked straight

4) reach overhead and rotate arms like your gonna do a shoulder width chin up and then pull the arms towards the rear using your upper back muscles, and feel the lats stretch etc. Hold for 20 secs

5) hold your hands behind you back, pull shoulders down and back, and pull your head to one side, looking slightly upward to stretch the neck muscles, hold for 20secs, repeat on the other

Enjoy!