Because many of us are so used to carrying around tension, it can be difficult to recognize when our muscles are tense. Even when we scan our bodies for tension, we may overlook it because it feels "normal." In order to increase your awareness of tension, you have to learn to recognize it. Try intentionally tensing a muscle for 5-7 seconds and then quickly releasing the tension while paying close attention to the sensations of tension and then relaxation. Relax each muscle for about 30 seconds. (This is best done lying down so you don't have to rely on your muscles to support your posture). By doing this with each of our muscle groups, we can learn to more easily identify and release unnecessary tension throughout the day.
Not sure how to tense a certain muscle group? Check out this chart.