Emulate Drag Playlist Folder to Make New Playlist
You can use the "Duplicate" option in a playlist's contextual menu to make an exact copy of the selected playlist. This works for regular and Smart playlists. You can also select a playlist and drag it in the Playlists section of the Source list to duplicate it as a regular playlist. Using this method will duplicate any kind of playlist as a regular playlist. This is especially useful for making a playlist from a Playlist Folder, which does not have "Duplicate" in its contextual menu.
But you may find it easier to run a script on a selected playlist to duplicate it, especially if you aren't wild about the drag-and-duplicate method which can be slippery. The script below will duplicate any selected playlist as a regular playlist. The new playlist will have the same name as the selected playlist, but you can edit this to include " copy" or something if you wish:
tell application "iTunes"
set selectedPlaylist to view of front window
set newPlaylist to (make new playlist with properties {name:(get name of selectedPlaylist)})
duplicate tracks of selectedPlaylist to newPlaylist
reveal newPlaylist
end tell
(The last command to reveal selects the new playlist; you may not want this.) Name it whatever you like and Save it as a compiled script in ~Library/iTunes/Scripts/. I've found this very handy for making playlists from Playlist Folders that contain several playlists (or sub-Playlist Folders of playlists). Works great with a keyboard shortcut.