Yah - when you import, make sure that the ID3 tags (seen when you Get Info on any given song) are matching. This is normally no problem if you rip from CDs, as the CDDataBase identifies most of the ID3 info from the CD. Sometimes you rip a CD that's never been ripped before and CDDB doesn't know what it is. Then you have to enter the info manually (and send it in to be a helpful, responsible member of the online community).
If you downlaod music, the ID3 tags can be all over the place - there's several CDDB-type servers which iTunes doesn't use bu other programs do, and some people put their own ID3 tags on everything and put them up to share.
Suggestion? Make a playlist of all the songs of a particular artist. Select all of them, and Get Info (it'll say "edit multiple items?" say yes) and the Get Info screen will look weird. It will show blank where ID3 tags are differring or where there aren't any. I just make everything blank except artist, album, track number, etc - I take off genre, Disk # (put that in the tile of the album), compilation.
In short, your iPod setup closely matches your iTunes setup. Clean up your stuff in iTunes. if you have a big enough iPod, set it to automatically update everything.