[gmku]

I tend to just go with what's on the jacket sleeve/LP spine. If it says "Mothers" instead of "Frank Zappa and the Mothers", for example, it would go in the M section.

I alphabetize by the first letter of the first word in a band's name disregarding articles (e.g., The Beatles go in the B section), but individuals usually by the last name (e.g., John Lennon in the L section).

I'm guessing this is what most of us do.