How do you sort your LPs?

Genre, then alphabetical order....for example, jazz, blues, rock, disco, military marches, soundtracks, disco, easy listening, classical, country, folk, etc. Have MOFI separated on their own racks, as I do Nautilus, DCC, Simply Vinyl, Etc. It’s a long process and is still something I am trying to keep up with, but the occasional flea market, record store, or on line purchases are accumulating faster than I can sort. And, coworkers, family, and friends who have given me boxes of records, I am still sorting those as well. In Germany, my old neighbor gave me a box of classical Deutsche Grammophone records. 

Just make it easier on yourself and not over think this and just do it alphabetical.

while you are at it....make a spread sheet of what you have also and can update as you add to the collection.

Alpha.
Genre is too hard as Eric says, too many artists fall into possible 2 or 3 genre's depending which way the wind blows.

I suppose it also would make a big difference according to the size of your collection and how often you add to it.

Genre, then alphabetical order