Proper head alignment means your ears should be in line with your shoulders. Anterior head carriage, where the head juts forward, is caused by excessive kyphosis or a curvature of the thoracic spine, which you may know better by the phrase, "rounded shoulders." While the condition can have many causes, including osteoporosis, one reason it is so prevalent today is because people spend hours spent hunched over a computer. Anterior head carriage is not just unattractive, it also strains the upper vertebrae and can cause muscle tension, chronic pain and even headaches.
Your Mom may have constantly been at you to "pull your shoulders back." Doing this consciously can be difficult, and it could even cause soreness in this area, especially if you don't have the shoulder strength to do so naturally. If you carry your head anteriorly, you need to strengthen your posterior deltoids, trapezius and rhomboid muscles. To do this, try exercises such as the reverse fly or a variation of the bent-over row where your elbow is out to the side -- instead of tucked into your body -- and your palm faces back. The trick is to squeeze your shoulder blades together at the top of the move or, if that's too difficult, squeeze them before you start and maintain the position throughout the movement. Many people find that they have to start with a very light weight due the excessive weakness in these muscles.
Anterior head carriage isn't just a condition of the non-exercisor. Many people who engage in heavy workouts neglect to equally work opposing muscles. Overly developed pecs and ab muscles can also lead to shoulder rounding. Exercises that work the rear shoulders, such as the fly mentioned earlier, counterbalance the pecs. The muscles opposing the rectus abdominis are the erector spinae of your back. Work these muscles with back extensions while lying prone on a Roman chair or over a stability ball. To overcome an imbalance in these areas, don't increase weight, repetitions or sets for the stronger muscles until the weaker muscles have caught up.
In between workouts, do postural exercises several times a day. One simple exercise is to tuck your chin and pull your neck back, holding it for five seconds. Another is to lift your arms out to your sides so that your elbows are bent at 90 degrees and positioned just below your shoulders. Pull your elbows back, squeezing your shoulder blades together and then relax. While sitting at your desk, roll your shoulders back and then press them down. Simply pulling your shoulders back, military style, actually causes your head to jut. However, pressing the shoulders down brings it into alignment.
Good posture requires not only strengthening the muscles at the backs of the shoulders and in upper back but also stretching the opposing muscles that could pull you into a rounded posture. Stretch your pecs by clasping your hands behind your back and lifting your extended arms up and away from your body. Stretch your abs with a modified cobra pose, placing your forearms on the floor and lifting your shoulders and chest. If you have osteoporosis, this stretch may put too much pressure on your spine. Instead, fully extend your arms in front of you, palms down, for a slighter lift.