You have a new venture in mind. And you've crafted a business plan so detailed it's a work of art. Don't get too attached to it.

As John Mullins and Randy Komisar explain in Getting to Plan B, new businesses are fraught with uncertainty. To succeed, you must change the plan in real time as the inevitable challenges arise. In fact, studies show that entrepreneurs who stick slavishly to their Plan A stand a greater chance of failing-and that many successful businesses barely resemble their founders' original idea.

The authors provide a rigorous process for stress testing your Plan A...