I plugged my new nano in and it transfered all the songs on iTunes over to it. Now I want to remove alot if not most of them and only keep the ones I really listen to. How do I do that?
I assume you're talking about removing songs from the iPod. Set the iPod preferences to manually manage the content, then go to the iPod in your source list and drag off the songs you don't want.
1) remove them from your iTunes library
2) Set the iPod to Sync only selected playlists and put the songs you listen to in the playlists you sync.
3) Do what WildCowboy said.
Note that you lose some functionality if you go the manual route. You won't get updated playcounts or last played dates and you won't be able to rate songs on the iPod and transfer that back to iTunes. You do get the ability to connect your iPod to a random machine w/iTunes and listen to the music on your iPod though.