How you delete content from your iPod depends how you have it set to update:
If you are updating automatically then delete the files from the iTunes library and next time you connect they will automatically be deleted from your iPod. Highlight the file and press the delete key on your keyboard, or right click and choose either Clear or Delete, depending on which version of iTunes you are using.
If you are updating manually, connect your iPod and click on the icon when it shows in the iTunes 7 source list click on the chevron (the little triangle) to the left of the iPod icon This will display the various icons for the iPod itself, Music, Movies, TV Shows and Playlists. Click on Music and you'll see the traditional song view. Find the files on your iPod that you want to remove, highlight them and delete directly.
To select multiple items such as all the songs in an album, click on the first track in the list hold down the shift key and click on the last track to highlight the selection. Then press the delete key.
To summarise, you start by highlighting the song/video/selection in either the iTunes library or on the iPod song list as displayed in iTunes then press the delete key on your keyboard:
Deleting songs or playlists from your iPod
There are also a couple of ways that do not involved deleting from iTunes. The default iPod setting is automatically update all songs and videos when connecting to iTunes. You can keep the automatic update setting and select "Sync Music - Selected playlists" then all you need to do is remove the song from the chosen playlist(s) and update, it remains in your library should you want to add it in future. You can read more about playlists at these links::
iTunes: Creating playlists of your favorite songs
How to create a Smart Playlist with iTunes
Loading songs onto iPod automatically
Another way is to choose the "Only sync checked items" option in the iPod Summary tab. By un-checking a song in iTunes, it will not be updated to the iPod and if already on the iPod, unchecking the song in iTunes will remove it from the iPod during the next update with iTunes. To stop unchecked songs being updated you have to choose that setting in the iPod Summary tab, unchecking the song in iTunes isn't enough.
Using unchecking to manage an iPod is an option but only if you can live with the other things unchecking does:
Unchecked songs will be skipped when playing songs from the library or a selection. They will only play when individually clicked on.
Smart Playlists have an option that unchecked songs won't appear.
Unchecked songs will not be burned to CD.
