Us tag nazis usually get our 'official' tags from MusicBrainz. That's a good start. Another thing I'd like to see ASA do is calling the Last.FM API and using the redirections from their site on the scoreboard so that popular, lazy tags like 'Motorhead' are automatically redirected to 'Motörhead'. lrn2charmap.exe, you lazy Americans ...

Classical music gets difficult though, as there are way too many ways to tag a song and it will never be 'wrong'. The only time I consider a tag wrong is when the composer is in the artist tag instead of the performer(s). (There is a composer tag, use it! Or add him to the song title if you have to.) Beethoven never released a CD, so give credit to the symphony orchestra please. You wouldn't tag a Coldplay song with 'Chris Martin' either.
(Also, while we're at it: do yourself a favor and don't rip YouTube videos. Their audio quality is an insult to my ears. Go with SciLor's Grooveshark Downloader instead.)