When you have an injury, it can seem like it follows you around everywhere.. in the office, out and about in town and also on your yoga mat.
I turned to yoga when I hit a low point with a shoulder injury and became hooked when I realised how much my mobility increased over time with careful practice.
The below article offers some useful tips for tight shoulders. Keeping the shoulder in its socket can be good advice for anyone, regardless of whether they are prone to injuries.
Personally, I find that actively pulling my shoulder blades back also can be a great help, as can careful spacing of the hands in downdog and in sun salutations. Turning your hands slightly to the outside, slight external rotation of the shoulders, in downdog can also be a help.Always avoid “hanging” in your shoulders in a chatturanga or plank pose, bringing the knees to mat if necessary.
http://www.yogajournal.com/beginners/shoulder-tightness-pain-or-injury-heres-the-yoga-that-helps/