How can I get/force song Info to sync with my iPod?

After importing a CD, I sometimes make changes to song info in iTunes, e.g. filling in a blank artist or composer. When I then sync with my iPod, these changes do not seem to be replicated. Why not? I tried unchecking the albums, sync'ing, and then re-checking the albums and sync'ing again, and that did not help. Bottom line: I see the changes I made in iTunes, but not on my iPod. Is there a way to force this song/album info to sync?