I was confused for a long time about my where my shoulder point was. I posted a question about it on the boards (http://sewing.patternreview.com/cgi-bin/sewingclasses/board.pl?t=13871) and found that some other people were having the same problem. I googled shoulder anatomy and found some useful info that I thought I'd share here.
The shoulder point in pattern making is actually the AC joint (acromioclavicular joint). This is the joint between the collar bone (clavical) and the tip of the shoulder blade bone (acromion). I was mistakenly marking the joint where the head of the arm (humerus) enters the shoulder socket! I found my AC joint by running my fingers along the top of my collar bone until I felt a little dent. I'm pretty confident that I've got the right spot now, even though I still don't see that 'dimple' at the hinge point that I keep reading about!
The photo I linked to was the least graphic photo for those who might not like that stuff, but if you google AC joint there are some more helpful images out there.