I'm definitely a newbie here and don't want to claim to have all the answers, but I just finished reading a book which people with AS might find helpful. The title of the book is "Pain Free" and the author is Pete Egoscue.
The central idea of the book is that much pain is caused by misalignment of bones in the body. I realize that AS pain is also caused by inflammation, but he mentions AS in the book and claims (though I think he's going too far) that doing the exercises can prevent spinal fusion in AS.
There are exercises for different body parts. Since my neck pain is the most bothersome to me, I started out doing the exercises for the neck. Like most westerners, my head is too far forward putting excess strain on my neck. I knew that already, but didn't know how to fix it. It's really interesting because most of the exercises for the neck focus on the hips He claims that neck position is based in the hips. The first time I did the exercises, I checked my posture when I was standing with my heels, butt and shoulders against a wall and allowed my head to go where it went naturally. Your head should be touching the wall in that position, but mine was about three finger widths away. Next, I did the exercises which involved things like lying on the floor with my lower legs on the coffee table and lying with my legs up against the wall. Afterward, I checked my posture again and my head naturally went to less than on finger width from the wall without any effort on my part. In fact, my posture had changed so much that it effected my balance for the first few minutes. I do the exercises in the morning and find that the effect wears off as the day goes on, but every day my posture is better for a longer period of time. There is less stress on my neck muscles and the pain in my neck is diminishing.
There are also exercises for other body parts, like the back, knees, hips, etc.
Egoscue also has a website, www.egoscue.com
Since posture is so important in AS, I thought some people might find this helpful.