"I have a question sort of on the subject.  Every once in a while I put together a figure with a prop that I want to mirror on the other side (ex., shoulder pad or horn), but I don't know how to position it strictly.  I'm always forced to approximate by eye.  Any way to figure out how to mirror a prop bilaterally so it's exactly where it's supposed to be?["

Answer: As long as the figure is "zeroed" (IE, centered in Poser space with X and Z = 0), and is in a default (symetrical) position then it's easy...

Load and position one prop. Don't parent it yet. With the cursor in the Parameters dials (best to click on a blank space there to make sure it's selected), select Menu->Copy (short-cut is usually ctrl+C in Windows). This will copy the complete set of the dials.
Load 2nd prop. "Select" the parameter dials for the 2nd prop and Menu->Paste (ctrl+V), which will place the 2nd prop in the identical position to the 1st.  Go through the dials and add or delete any relevant "-" signs for position/rotation. So if, for instance you wanted to put a cube/box on both shoulders of a figure, you could load and position cube 1, copy the dials, load cube 2, paste the dials into cube 2 then change the X-trans to the opposite side (if it already has a minus sign delete it, if it doesn't add one),

THEN parent both props to the relevant parts..

 Hope that makes sense..

Cheers,
Diolma