Q: How can I save a pose that applies to only some parts of a figure?

A: Click the "+" in the pose palette as you would to save a normal pose. In the 'New Set" box that pops up, click the 'Select Subset" button. In the 'Select Objects' click on 'UNIVERSE', this will clear all items from the pose. Now click in the body parts and/or parented props that you want to include in the pose. Click OK, give your pose a name, and proceed as when saving a normal pose.

Q: How do I save a pose for a prop?

A: as above but only include the prop. Note that such a pose can only be applied to the prop whilst it is parented to some figure.

Q: Can I apply a pose to a prop when it is not parented to a figure, and when there is no figure in the scene?

A: Not normally.[For advanced users] However you can do it if you are willing to get your hands dirty in a text editor, and hack the pose file. First make sure 'Use file compression' and 'Use external binary morph targets' are turned off in your General Preferences. Parent the prop to any part of a figure. Save a pose for the prop as explained above. Open the resulting pz2 file in a plain text editor (eg EditPad Lite, or NotePad++). Use the editor's Search & Replace function (called "Find & Replace" in some editors). Set the Search string to "prop " (include a blank space after the word), and set the Replace string to be "actor "  (include a blank space after the word). Execute a case sensitive  Search & Replace. Save the file to a Camera folder with a '.cm2' file extension. The point of saving as a cm2 is that a pz2 pose can only be applied if there is a figure in the scene, but a cm2 can always be applied. The above works for any type of pose.

[the tips in this post work for any Poser version form at least P4 up]