here are some key things to note when digging:
1. Ugly person on cover = really great vocals
2. If the persons head is a fruit, or the album contains some sort of fruit, they're jazzier than jeff
3. Afros seem to signal drum breaks, and spaceships signal good records.
4. And if an album has puzzles, or a visual trick, those are usually tight albums.
5. NEVER pick up an album with a picture of a man on a farm... trust me, it's for your own good. Especially if he has a pitchfork.
... i guess this is just speculation on the most part, and might not be true so use at your own risk.