Make an on-the-go playlist:

  1. Tap Playlists and tap On-The-Go.
  2. Browse for songs using the buttons at the bottom of the screen. Tap any song or video to add it to the playlist. Tap Add All Songs at the top of any list of songs to add all the songs in the list.
  3. When you finish, tap Done.

    When you make an on-the-go playlist and then sync iPhone to your computer, the playlist is saved on iPhone and in your iTunes library, then deleted from iPhone. The first is saved as “On-The-Go 1,” the second as “On-The-Go 2,” and so on. To put a playlist back on iPhone, select iPhone in the iTunes sidebar, click the Music tab, and set the playlist to sync.

Edit an on-the-go playlist:
Tap Playlists, tap On-The-Go, tap Edit, then do one of the following:
  • To move a song higher or lower in the list, drag next to the song.
  • To delete a song from the playlist, tap next to a song, then tap Delete. Deleting a song from the on-the-go playlist doesn’t delete it from iPhone.
  • To clear the entire playlist, tap Clear Playlist.
  • To add more songs, tap .

Source: apple.com