Random Charts & Tables
One of the first things that comes to mind when I think about old school style RPGs is all the amazingly fun random charts and tables they had. It seems that nearly everything in AD&D, Rolemaster, RuneQuest, and even their ilk was represented by some sort of table. Critical hits, monster summoning, wandering monsters, treasure, even dungeon corridors all had their own randomness.
I remember spending more than a healthy share of time playing with random tables. Creating totally random dungeons with tables and then populating them with tables and assigning treasure with tables. The tables were everywhere and then they started making books of nothing but tables. The first of these I have solid memory of was the Armoury book that came with their first D30 die. This book was full of interesting random rolls to determine all sorts of obscure things. Later on there were even books to help you randomly generate the background of your PC.
The fondness for random tables has never left me and in my time blogging, I have even had a chance to create and post a good number of my own. I've listed a few of these posts below -
Random Things to Find When the Party is Lost - http://leadpeople.blogspot.com/2010/02/30-random-things-to-find-when-party-is.html
Kingdom Problems - http://leadpeople.blogspot.com/2010/02/30-crazy-kingdom-conundrums.html
Mysterious Animals - http://leadpeople.blogspot.com/2010/02/30-mysterious-animals.html
Femme Fatales - http://leadpeople.blogspot.com/2010/02/30-flawed-females.html
Odd Halflings - http://leadpeople.blogspot.com/2010/02/30-odd-halflings.html