Having just got my iPod about 6 weeks or so ago, and having done the usual thing of loading loads of music in one long weekend hit, I have lots of tracks that aren't rated.
I decided to create a playlist that plays all unrated tunes and then I can rate them as I listen, slowly whittling down the list.
Create a Smart Playlist:
Rating is less than 1
Last played is less than 7 days
Comment does not contain 'mixed'
Note - that last criteria is because I have a lot of mixed dance cd's on the iPod and I don't rate individual songs - just the whole CD.
Final point - I also give every song that I'm not sure about 1 star, and then after I have cleared my original list I can go thru the 1 stars and decide whether to delete or not..!