If your iPod is set to automatically sync content from your iTunes library, you configure these tracks to no longer sync to your iPod. In order to figure out how content is set up to automatically sync to your iPod, you'll want to see what options and configurations you have set up from under the iPod's Summary and Music tabs. You can access these tabs by plugging your iPod in and selecting it from under Devices when it appears in iTunes.
For example, if your iPod is set up to sync only checked songs and videos (this option can be found under the iPod's Summary tab), make sure the tracks you no longer want on your iPod do not have a tick mark next to them in your main iTunes library.
Othewise, if you manually manage the iPod's contents (i.e, the manually manage music and videos option is enabled from under the Summary tab), you must manually remove the tracks from the iPod via the iTunes interface. With the iPod plugged in, click the small black triangle next to it from under the Devices section in the left hand pane to reveal a submenu containing the different types of content synced to your device. Select the Music option. Then highlight any tracks you wish to remove from the iPod and either:
- Hit the Delete key
- Choose Edit -> Delete
- Right->click (control->click on a Mac) and choose Delete