A shoulder strain can occur traumatically or because of a repetitive activity. Typically you’d be feeling pain during movements of your arm if a muscle is strained. Gentle stretches, and gradually adding in strengthening exercises will get your shoulder back into action.
If your shoulder hurts and it’s not demonstrating a specific concern (see “related”), or if it doesn’t hurt and you want to make sure to keep it that way, then a well rounded stretching and strengthening routine that focuses on joint alignment is a great place to start. This program will give you a comfortable combination of exercises that work on flexibility and stability that take the edge off a painful shoulder and offer excellent support to keep your shoulder injury free in the future.