If you want to do it properly you have to consolidate the iTunes Library. By doing this you effectively keep all the old settings as well, including playlists, ratings etc.
File > Library > Organise Library, then Consolidate library.
You are then left with one folder with everything in, and if done correct devices that were synced with the old library will still work fine.
More info:
http://support.apple.com/kb/HT4527