**As of April 2012, this tutorial has become obsolete. To use this feature without going through tedious steps, please use this great mod.**
This tutorial was done by me a long while ago when I discovered that some poses could look different depending on where the Sim was focusing last before freezing into the assigned pose.
It may be useful for some of you, and it helps you understand why some poses may look slightly different, such as the head turned elsewhere. You can then use that to your advantage.