Having wandered through the land mine that is Poser animation, Ive found that the best way to approach this is one body part at a time. Go through your animation and set your largest body parts -- hips, abdomen, and chest -- first, and click on the "add keyframe" button only after youve set "body", not "body parts". Stop and check it for rough movement. If it looks good at this point, then work out from there to the arms, neck, and head. If youre doing any mouth movements, do them last (trust me on this one).