Make Playlist Folders
If you like to have a playlist or five for every occasion, but find your iTunes Source list is getting crowded, iTunes lets you store multiple playlists inside convenient folders.
❶ To add a folder to your Source list, click the Source list's Library icon and then choose File→New Playlist Folder.

❷ A new "untitled folder" appears, inviting you to change its name to something more original, like Dinner Party Playlists.
❸ Drag any playlists you want to store inside the folder onto its icon.
If the whole family shares one computer, folders can give each person a tidy receptacle to store his or her personal playlists. Folders are also great for storing a bunch of playlists that go well together. That way, when you select the folder and hit play, iTunes plays all the folder's songs consecutively.

Note
Great news for iTunes Veterans. Back in Ye Olden Days, iTunes used to dump all your playlists-inside-a-folder into one massive playlist (using the folder name) onto your iPod. No more. Now, once you sync your iPod, you end up with a folder's individual playlists all right there on your iPod.