there's probably an easier way to do this but i have found this to be helpful. let's say ur building a scene or an animation and you want to add another pose to a character from the pose library, but ur character has moved. when u add the pose he moves back to the zero position and rotation.  when u move your characers to make a new scene i find it is a good idea to move everything to a new keyframe. then when u give a character a new pose just go to his hip and press the arrow to get the different hip prameters. Encircle with the cursor any hip parameters u want to keep from the first frame (probably xtran, ytran, and ztran (maybe y rotate) and drag them to your new keyframe and the position of your character will be restored with the new pose.

Computer Art by Charles McChesney