If it's what to do to counteract a possible negative event crisis, that's simple. Don't overnight longs. Only overnight shorts. I simply go to cash at the end of the day, unless shorting. IMO the rewards are not worth the risk to long overnight.
Just don't hold long over a weekend, especially a long weekend! Many Friday afternoons there is a dump into the close.
Make sure your stops are always in. (A few weeks ago I had some MER options that were at a nice profit. Bang, power in neighborhood goes out. By the time I got back in they were red). You can always hold some OTM index puts as extra insurance.
watch, MAGS, mace,ipix when terror threats are likely . they run up when fear is greatest imo. when market goes up , they go down imo
And if Osama Bin Laden is captured, and you're holding an overnight short, you'll be screwed royally as well. That's about the only "disasterous" scenario I can think of that would dramatically make the market skyrocket. Think of any others?