what is the best way to backup my ipod touch

iOS: How to back up and restore your content

However, the:

iTunes backup does not included any synced media like apps and music

- The iCloud backup does not included any non-iTunes synced media. Also, if the iTunes purchased media is not not currently available for iTunes it can't be restored.

- For synced media see:

Recovering your iTunes library from your iPod or iOS device: Apple Support Communities