I store my favs and special editions on shelving alphabetically. The rest are taken out of there casing, this is then stored in cardboard boxes. The discs are then put into cd aluminium DJ cases. The benefit of this is there easy to sort through and find.
I bought 5 of those "72 DVD/CD HOLDER WALLET" things and a couple of 36 as well and put all my DVDs in them and all the DVD boxes now put away in the loft
one wallet is comedy another is Sci-Fi and horror and another is Blu-Ray , you get my drift
Now I can find any movie I own in less then a minute
Top shelf - split 50/50 Vampire/Zombie
Second shelf - Other horror/18 rated action.
Third shelf - Hong Kong action
Fourth shelf - Comedy/TV shows/Other action
Fifth shelf - Animation and everything else.
Don't ask me why I keep the 18 rated stuff out of the reach of children, when I have none
Guess it's just so that I don't have to bend down when I need my "gore fix"
By mood. Mostly this means that it appears to be grouped by genre; but there's some films that defy the genre definition and fall under another mood which they elicit in me.
I have two aluminium DJ cases, one which fits 510 discs and is full and another with a capacity of 300 that currently has around 80 discs in it. I also keep about 70 discs such as the Alien Quadrilogy, the Hitchcock collection, the Bond collection etc. in their boxes which are on my shelf. The boxes for all the other discs are kept in my wardrobe.
All of my Blu-rays and HD DVDs are currently in their boxes on another shelf but I'm running out of space so they may have to be resigned to a DJ case in the near future.