I've been playing various forms of RPG's and games off and on since the mid 1990's. The game I'm probably most familiar with, or at least most experienced with, is Advanced Dungeons & Dragons, particularly 2nd edition. Lately I've been reading a lot about what's being called the Old School Revival (or OSR for short). In having done some research into the movement, I've discovered there really is no true definition of what constitutes an "old school gamer." Instead there are a myriad of theories on what separates "old school gaming" (D&D 0e, AD&D 1e, some 2e) from what's considered "new school gaming" (3e, 3.5, and 4e AD&D).
The best description on the differences between the two schools of thought can be found via Matthew Finch's free pamphlet, "A Quick Primer for Old School Gaming." Mr. Finch is the creator of the 0e "clone" of DnD called Swords and Wizardry. In his Quick Primer, he presents four situations, which he calls "zen moments"
The first of these "zen moments" he calls "rulings, not rules." In this scenario, the old school GM/Gamer dialogue centers around the gamer using his own wits as a player to perform an action rather than the "new school" method which is to say, declare an action and simply roll for it based on the character's abilities according to the rules. In the old school approach, the game is more dynamic and involving rather than a situation bound upon dice rolls and chance.
The second zen moment is a bit redundant, but notes that in old school gaming, player skill is more important than character skill. That is to say, in an old school game, the player must use his own wits to figure out a scenario. There are none, or at least very few, "checks" to determine if something is successful. The player announces what he wants to do and the GM makes the decision on this action. The player's skill comes into play above the numerical abilities of a character from a rule book.
The third zen moment is the realization in old school gaming that the character will never become super human, but rather will become heroic. He compares the notion of the character eventually building up through play to become Batman rather than Superman. In other words, the player character is still a mortal. The only thing that separates him at a high level from what he was at a low level is the things he's been able to accumulate and the experience he's gained through the years.
The final zen moment he describes is the act of forgoing game balance. That is to say, there is no such thing as game balance in the old school gamer's world. There is nothing which states that a character may only encounter those foes and traps which he is able to defeat. There will be situations in which sometimes you come upon a situation in an old school game that you're not skilled enough to complete. There's nothing in an old school game stating that your character won't encounter a high level mage, beholder, or even a dragon at a lower level.
There is more to Mr. Finch's assessment of what constitutes old school gaming, of course. Essential at the heart of the distinction is the player using his own skills to deduce the GM's intentions rather than relying on dice rolls, rules, and ability scores. These are tools to be used, but not relied upon for every situation.
I've tried to look at the arguments for what constitutes "old school" and "new school" gaming to see just where me and my friends fit in. We've all been playing D&D off and on together, as I said, for nearly 20 years. I think it's safe to say we are somewhat of a hybrid of the two. Old school games in general simply relied on dungeon running, gaining treasure, and creating heroic memories through the use of well thought out and well played scenarios and encounters. The new school approach relies on the accumulation of power, vast campaign settings from a corporate entity (WoTC), and dice rolls to determine success.
In my near 20 years of playing D&D, I've spent sufficient time as both DM and player. When I was first introduced to the game, it was by a purist old school gamer of 1e. He didn't spend a lot of time on character development and the like. He was a hack and slasher and a dungeon crawler, but as a DM his adventures were always exciting. As I started getting more and more into 2e and the products TSR produced such as the Forgotten Realms sourcebooks and settings, I became more interested in making characters with heroic personalities.
These days in the current game I run, a 2e game based in the Realms, the game goes much in the direction of a hybrid between old and new school. Yes, we use character ability rolls and checks. That's what they are there for, however each situation is approached with caution and care. For example, you won't find any of our players running up to a door and simply saying "I look for traps *dice roll*. I got a 20. Are there any traps?" Rather each encounter is thought out and discussed in as much detail as possible and, when necessary, the dice roll is made to ensure success.
Also, as a DM I encourage my players to take an active role in determining how their stories will turn out. Most old school DMs would scoff at that notion citing that the DM should always have control over the game. I always ask my players to create some sort of background for their characters for me to work on as a DM. I then can incorporate these particulars in the adventures that play out. It adds a bit of extra depth to the sessions and also helps them discover who their characters are and what drives them. Is this a new school approach to gaming? Probably so, but it works for us and we enjoy it.
It's difficult to draw any pure distinction between old school and new school gaming other than the fact that most old school advocates do not approve of or participate in the play of 3e, 3.5, or 4e D&D and to a lesser extent, 2e. Or perhaps they do participate, but don't feel the same magic they felt when playing prior versions of the game as they did in their youth when there wasn't a rule to determine how each and every thing would work in the game. Most gamers probably want to associate themselves with the old school because it gives them a sense of credibility among their peers. A way to say, "I've been there and done that." Bottom line is, everyone who played earlier editions of the game, has their own viewpoints on what constitutes "old school gaming." We as gamers should not be bound to these terms in a negative connotation.