This is a pretty interesting (free!) resource: the quick primer to old-school gaming! It contains a few tips on how to compare and contrast (in the author's view) the different mentalities behind older (read: D&D circa 1979) and newer (read: anything you can buy at Borders) RPGs.
Incidentally, it's tied in to the Swords&Wizardry rules set. I'm tired and it's a little hard to explain (the word "Zen" gets used a few times), so I leave you to this sweet, free download.