( when your iPod shows up in Devices in iTunes)
1. You can choose which music to sync from the 'Music' tab. Select your iPod in 'Devices'. In the Music tab (your device page will show your options), you have choices to sync entire library, sync selected artists, albums, genres and playlists. You can also choose to fill any empty space with songs (random).
Further down that page, you can check (uncheck) which artists, albums, playlists etc to sync to that device.
Making playlists (and selecting/deselecting) makes for a much faster way to add music and variety.