Glad I found this thread, I'm getting my NASM-CES and have been reading all about this topic because it applies to myself. The way my textbook describes APT is that you're glutes are generally under-active, this gets compensated for by over-strengthened psoas and other anterior hip muscles.
I've found my hamstrings have always been extremely flexible, I have always found various hip flexor stretches helpful.
"Yeah, NOT hyperextending the lumbar spine is the first skill to learn.
Once you have progressed, the goal is NOT to move out of spinal neutral."
When you say hyperextending the lumbar spine you mean over-rounding?
Here's a quick DL video, what do you think of my back position here?
Notice the idiot doing karate in the backround, lol.