There is a fantastic free book available on Lulu called Quick Primer for Old School Gaming. It succinctly details the differences between modern and old-school roleplaying. It outlines four “Zen Moments:”
- Rulings, not Rules
- Player Skill, not Character Abilities
- Heroic, not Superhero
- Forget “Game Balance”
Numbers two and four, for me, best encapsulate what is meant by “old-school.” In modern play, players are likely to simply say, “I check the room for traps,” and the DM simply asks for a skill check of some sort. This doesn’t require any thinking or creativity. Furthermore, modern play implicitly assumes that a party has a reasonable chance of making through it any given combat encounter; the concept of retreating for fear of being overpowered or to conserve party resources, is foreign to many modern players.
Check it out; it is definitely worth the read.