For example: A man walks into a department store. It's been a slow day for a sales clerk who works on commission and he needs at least $100 to make his monthly goal. The clerk asks the customer if he wants to try on a pair jeans. The customer refuses and says he is only browsing because he does not what to use his credit card for the purchase.
"What if," in spite of this example, is not a form of manipulation. It might be in some scenarios, but that is not the ultimate aim of this technique. Instead, it is a way that Clerk and Customer create a path to achieving what they each want in the scene: Clerk wants to make a sale; Customer wants to browse. The stakes are clear-- earning $100 versus not using a credit card-- and these contending desires create a foundation for the magic "what if."
What if... Clerk brings over a rack of deeply discounted jeans and offers the customer an additional 10% off the entire purchase? Or what if the clerk places the customer on a email list that instantly offers him a buy-one-get-one free coupon?
What if... Customer gets out his phone and calls a friend while in the store? What if he actually plans to rob the store later that night before closing and is only casing the store for cameras, exits, and alarms? What if the customer discloses the truth and explains that he has no extra money right now?
Do any of these choices change the scenario and get either character closer to what they want? Each scene is not necessarily a hatch mark towards an answer; after all, characters are sometimes no closer to what they want than when a show first begins. But, "what if" is a nifty technique that helps unfold a deeper context of one's character and builds a path towards fulfilling his/her wants. Try it out...it works in real life too!