Don't use iTunes to rip music from a cd unless you have a specific audiophile-esque reason to do so, I recommend (its free), once the file is ripped you can then add it to your iTunes library.
Generally speaking, you should rip your music to mp3 at 192kb - its the best tradeoff between sound quality, file size and compatibility with devices.
If this all sounds too hard, iTunes @ 192kb mp3 is your best bet. If you use the white earbuds that came with the iPod, then it doesn't matter what you do