Meaning: expecting the next step to occur, usually with negative consequences. Use examples.
Rewrite 1: waiting for the other door to slam
Rewrite 2: waiting for the over-weighted shelf to fall
Rewrite 3: waiting to see where lightning strikes next
Rewrite 4: waiting in line at the will-call window, but hoping they're sold out

Comment 1: The more explanation you have to build into the phrase for it to make sense the less effective it is as a metaphor. Rewrite 2 above is close to being too long, although I think it still works.

Comment 2: This cliché has shown up most recently in the wake of the Jack Abramoff scandal. It was frequently used to describe the fear members of the U.S. Congress and many of their staff feel as a result of Mr. Abramoff’s plea bargain with prosecutors. It was used so frequently, I decided it was an appropriate time to offer some alternative phrases. Thus, this entry.

More reading about clichés
What I found when I googled “clichés”:
• Cliché Quotes: “Clichés quotes and quotations from BrainyQuote.”