Alphabetical by title, generally. Titles beginning with numbers are before “A”. Series are together and in order. So, all of the Bond films are next to each other in release order instead of all over the place and The Road Warrior is next to Mad Max instead of under “R”. When the name of the series is different from the name of the first film, I put it under the series name, so the LOTR films are under “L”, not “F”, and the aforementioned Bond films are under “J” for James Bond and not “D” for Dr. No. For Star Wars, I’ve got official releases first, so it’s the GOUT DVDs, then the PT blu-rays, then the OT blu-rays, then the Despecialized blu-rays, then the Holiday Special. For Star Trek, I’ve got the TOS movie blu-ray set, then the Wrath of Khan remasterd blu-ray, then the 2009 Abrams film. I’ve got all of my Criterion discs on their own shelf organized by spine number.