maybe you could read the instructions.

uncheck the songs on iTunes (u kno from that little checkbox next to the name) they shouldn't transfer on next time you update your iPod

if you delete them from your itunes, and then update your ipod, that will do the trick.

on the library you delete or click on the song and it should give you like a box or something and scroll down or look for delete

or you could

In iTunes click in the box next to the name of the song you want removing and remove the tick. When you next connect your iPod to iTunes the song will be removed from your pod. If you want to add the song back to your iPod you can just tick the box again.
2. Uncheck the song(s) in your library. This only works if you have the "Only update checked songs" option checked in the iPod pane of the iTunes preferences.