I transferred music from one PC to another using Home Sharing.
The music all came through, but the ratings did not.
How do I make it move my ratings over?
I'm afraid you cannot do it, or at least you cannot do it via the home sharing mechanism at least.
Certain items of Meta data, (including play counts, last played, ratings etc) are not stored as a part of the songs own Meta data (Title, Album, Track number etc), but instead belong to the iTunes library as a whole. When you transfer a song using home share, you are effectively making a copy of it and placing it into a second library, where the flags are effectively zeroed out as if they have never been set (which, they haven't, for the new library that is).
That's just the way iTunes works, it all revolves around your library as much as the individual items within that library, so a play count would not copy over as it is not considered a part of the song itself.
You may be able to script up a method of transferring such library Meta data, but it's by design that you see this behaviour using Home Share. Tools may exist, but I'll leave it to others that may have used them to mention them as I have no relevant experience.