Step 1: Your Favorites
Simply put, there is no reason to have a DVD library that does not include those movies you love to rewatch. I don't care if your favorite movie is 8MM, if you love it then it belongs in your library. I suggest you make a list of your top ten favorite movies of all time. This is a good place to start, because in the process you will likely think of at least ten more that you really like. Keep a separate, ongoing list of these.
Step 2: Your Childhood Favorites
For some, these are guilty, nostalgic pleasures; for others, they're the crown jewel. Whatever they mean to you, you should indulge and add at least a few of them. My wife and I were excited, for instance, to add Howard the Duck to our library when it was finally released on DVD earlier this year. The younger you are, the trickier this is because of course you may not have had enough time pass that you feel that fondly about such things. Don't fret; because you're of the home video generation, you won't find many releases that you will have to wait decades to have when you decide you want them.
Step 3: The Things That Make Others Take Your Library Seriously
Now, it's important to note that I don't mean anyone should buy any movies for the whole purpose of impressing other people. That is not only financial absurdity, but it runs contrary to my longheld endorsement of individuality. No, I titled this step the way I did because these are the movies that were probably over your head as a kid and may not be among your top ten favorites. I only know one person who ranks Doctor Zhivago in her top ten, for instance, but would expect to find it in quite a lot of libraries (I know it's in mine). I suggest you start with the American Film Institute lists of the last decade or so, and rent some of the titles on them. If you find yourself really enjoying something, pick it up.
Step 4: TV Series
For me, this is the trickiest part of the whole process. I'm really not that likely to re-watch a TV season set, but I have found that DVD is my preferred way of watching a season. On a bleak day, my wife and I might do a marathon viewing of a season, though mostly we prefer to watch an episode or two each night until we finish a set. "But my favorite show is Friends and they re-run it seventeen times a day on four different channels," you say. Well, either skip Friends and explore another show or go ahead and sit down with the first season DVD release of Friends. It may surprise you how even watching an episode you can quote verbatim can feel different when it's exhumed from under advertising graphics and not interrupted every nine minutes.
Step 5: The Collectibles
Okay, this is the purely self-indulgent/show-off step. For a great many movies, there are various releases. Sometimes, one release replaces another; other times, they are release contemporaneously. Let's take the Indiana Jones series as our example. You might be like me; you enjoyed the movies enough to add them to your library, but that's about it. Here have been your options:
The Adventures of Indiana Jones boxed set - Contains Raiders of the Lost Ark, the first two sequels and a fourth disc of bonus material. Available in Widescreen and Full Screen Editions.
Raiders of the Lost Ark, Indiana Jones and the Temple of Doom and Indiana Jones and the Last Crusade - Special Editions, sold individually. Also collected in Indiana Jones: The Adventures Collection boxed set.
Indiana Jones and the Kingdom of the Crystal Skull. Available in single disc and two-disc special edition releases, and the single-disc release is also included in Indiana Jones: The Complete Adventures Collection with the previous three films.
Now, unless you're particularly into bonus features, The Complete Adventures Collection is the way to go. You get all four movies and the nice thing is that they're individually packaged in slimline cases, so the whole box takes up the same shelf space as two regular DVD's. But, of course, you might be into bonus material. The Adventures of Indiana Jones boxed set is the only place you'll find that fourth disc of bonus interviews and behind-the-scenes footage. On the other hand, the subsquent releases of the original three movies include bonus material