Being a perfectionist, I like to rate all my songs. I usually do this diligently while using my iPod, but sometimes I forget or can't reach it (eg. while standing on the bus). I've come up with this Smart Playlist to tell me what songs still need to be rated:
Play count -> is greater than -> 1 AND
My Rating -> is -> [empty]
One simply rates all the songs in iTunes (or even on the iPod if you've got the patience to skip through all the songs) until the playlist is empty.
A while ago, due to a hard drive failure, I lost all my ratings and play counts. I started manually managing my iPod and racked up a few play counts. When I got the computer up and running again, it meant that most of my songs now had a play count greater than 1 but were not rated, meaning that the above playlist listed way too many to face in one hit. To combat this, I've added the following criteria:
Date Last Played -> is in the last -> 1 -> month.
This gives me a month's worth. The songs played earlier than a month eventually show up as I relisten to them.