Do you have any special way you order your physical collection?

I have IKEA shelves, 4 stacking units, that I have placed side-by-side, two high, to create a nearly 2m-long, low unit with four shelves.

I had the entire collection ordered alphabetically by composer (classical, some ethnic) or performer (jazz and popular, some ethnic), without regard for genre.

I have categorized my collection into four genres: classical, ethnic, jazz and popular. This covers my collection well, without the need to make tenuous exceptions for some albums: categories fit logically. I call it Radio CEJP.

Lately, I had thought I might like to separate the genres, since I mostly play classical, so I wanted those on the upper three shelves (no doubling up, yet ), and the other genres on the lower one (partially doubled up). I stayed up until 3 last night getting it done. Wow! I like it. I no longer need to peer at floor level to get at Wagner or Xenakis.

How do you organize your physical collection? Do you have separate shelves for each genre? Even keep them in separate rooms for different types of listening? Do you have them on shelves or in stacks? How do you deal with exceeding the capacity or non-standard album sizes: get more shelves, double up, etc.? Any unique solutions?