[copeab]

I don't do zero prep (usually) but I do have little prep for a specific session. It has been my experiences that a GM who prepares in detail tends to railroad at worst and a lot of work gets wasted at best.

The only things I have to work out beforehand are:

1) who represents the challenge to the PC and what does he want to accomplish?

2) where are events going to occur?

Both of these can be heavily influenced by previous adventures in the setting.

There are also cheats: I picked up the Destiny Deck in the early 90's and it's a quick way to deal out basic story elements (Plot, Setting, Atmosphere, Bonus).

I have also picked up a bag of Rory's Story Cubes (9 six-sided dice with assorted symbols) a couple of years ago and while as well-suited as the Destiny Deck, they are available now. Plus they can be used in their intended role as a storytelling game for kids.