I unpacked an old book on it this year. Basically you hang your head down a lot. That's it. If you have CCI, or CSF leaks or Chiari, you'll get a little relief, true - but what you really need if that works for you is a neurosurgeon (not neurologist) and an upright MRI. In the seventies, there were no upright MRIs and nobody took chiari or CCI etc seriously so the Alexander Technique was all there was.

"Basically you hang your head down a lot. That's it."

That is the equivalent of saying that "meditation is just sitting there, thats it".

Most teachers agree that at least some hands on lessons are helpful if not essential. If you are going to try to learn from a book then this one is the best I heave read on the subject http://www.missyvineyard.com/content/view/1/2/.