I’ve heard this many times, and I think it’s a really cool way to decide what happens next in your story. Every time you’re character encounters a problem, you ask yourself if they overcome it. But the answer should not just be yes, or no and move on–instead it should be a yes, BUT or a no, AND.
Overly simple example:
Your character is in a room and wants to leave. She tries opening the door to leave.
Does she succeed?
Instead of yes, she opens the door and leaves, it should be yes BUT something. Such as, yes she opens the door and leaves but there is a hoard of mutants on the other side of the door.. or her mother in-law, or her ex-boyfriend, or any other not so good thing you can think of.
Instead of no, she can’t open the door and moves on to try a window, it should be no AND something even worse. For example no, she can’t get the door open and the knob is scalding hot and burns her hand, or the knob falls off completely, or the room begins filling with water, or her mother in-law steps out of the closet…
It’s a neat way to move your story forward in a more interesting way. Try it! Answer every yes/no question instead with yes, BUT / no, AND.