I thought I understood posterior pelvic tilt pretty well, but it's something I know I need to work on. I was working with a coach the other night doing, among other things, some work on 360 degree breathing. This was done from an all-fours position with full scapular protraction. At one point he said to me "bring your belt buckle to your chin".
I can't believe how much this one cue has helped me, especially when I'm in non-standing positions. It's been especially effective for hollow body rocks and forearm planks, and I'm finally improving my PPT while in a handstand.
Hope this helps.