Organizing your music library

Over the past few months I have tried to determine the best means for universally organizing my music collection for my iPod on-the-go. The problem is that different types of music are referenced differently, at least in how we think of them.

Here's a taste of some of the contrasting music styles that I have and the difficulties that accompany them. I've also listed my attempt at resolving them, though perhaps you'll notice the inconsistencies:

• Showtunes
• Artist = "Original [Broadway/London] Cast"? (although more vague, it seems more reliable than having the individual performers listed for each song)
• Album = show title?
• Year = recording (not release) year
• Soundtracks
• Artist = :"Original [Motion Picture] Soundtrack" (or similar)
• Album = "[movie/game/source] Soundtrack"
• Compilations
• Artist = source? (note the inconsistency this causes with treatment of soundtracks)
• Or should the song title include the title + source? Then what to do with artist?
• Album = compilation name?
• A Cappella
• Artist = group name (or heaven forbid, "A Cappella" or any of its variants)
• Genre = A Cappella? Vocal? Pop/Rock? 
• Classical/Instrumental
• Title = Only the piece's title? That leaves you with a lot of "Symphony No. 1"s.
• Artist = Composer? Or performing individual/group?
• Composer = Composer? Is it worth using the composer field?
• Songs by artist, not by album
• Should I remove the few tags that do have an album association?
• Do I simply deal with the "Unknown album/artist/etc" tags?
• Private songs
• How to tag songs that I'd like on my player when needed but not available for shuffle?
• Reserve a special playlist for these "gems"? Or just deal?

It all comes down to how to populate various fields, particularly those utilized by the iPod (Songs, Artists, Albums, Composers, Genres).

Any suggestions? Any and all are welcome.