What is the alexander technique?

As far as I know you need to enrol in some sort of class. Because the instructor will point out changes you have to make to correct your posture. Read this wiki.

Frederick Matthias Alexander was a Shakespearean orator who developed problems with losing his voice. After doctors informed him there was no physical cause, he carefully observed himself in multiple mirrors. This revealed that he was needlessly stiffening his whole body in preparation to recite or speak. Further, Alexander observed that many individuals experiencing voice problems tightened the musculature of the upper torso, especially the neck, prior to phonation in anticipation of the act of voicing; he suggested that this pattern of tensing would rotate the head backwards and downwards in relationship to the spine and disrupt efficient overall body alignment. Over the next eight years, he attempted to change this habit, after which point, he found that the pattern of voice loss had ceased.

See a recommended chiropractor.

The Alexander Technique is an approach to un-learning harmful habits in the use of the body. It consists of guided, hands-on lessons in which a certified teacher (who has completed 1600 hours of training) will work with you on common activities to help your body/muscle memory learn to move in the most efficient, effortless way possible. If you have hobbies, skills, or other common physical tasks (such as playing an instrument, fencing, etc.), your teacher can also help you learn to do those activities in a way that minimizes stress and emphasizes ease and range of motion, making them less taxing on your body. More information can be found here: http://www.amsatonline.org/