How can I drag and drop transfer a playlist of songs using home sharing?
Create a new playlist on your local machine with the same name as the one you would like to import.
Click on the library that you wish to import a playlist from over Home Sharing.
Expand the library by clicking on the arrow to the left of the name.
Expand the folder called Playlists from within the library.
Drag the playlist from the home sharing library onto the one you have created.  


Your music will be copied over into the new playlist.  This method does have one flaw, however.  If you already have some of these songs in your library, they will be duplicated.  But, File > Display Duplicates may help you with that.

Unfortunately, this is the only way to do this over Home Sharing.  Hopefully, iTunes 11 will improve on this, but I'm not getting my hopes up.