Conceived in the 1960s by sociologists Eugene Weinstein and Paul Deutschberger, the method involves characterizing people as certain personality types in order to nudge them towards a specific behavior. To illustrate, in a recent Wall Street Journal article Elizabeth Bernstein writes about how she persuaded her 7-year-old nephew to give her face-licking new dog a second chance by casting him as a "puppy whisperer." Similarly, in a business setting, mentioning someone's particular adroitness in a subject or activity will make them more likely to step up to the task.
The key to altercasting effectively is timing. You need to cast the person in a role before you make the request. In the new book Pre-Suasion: A Revolutionary Way to Influence and Persuade, Arizona State University psychology professor Robert Cialdini says the most important moment is the one immediately prior to the request. To ready a person to make a purchase, for example, Cialdini says you could have them write down a large number (one that's higher than the sticker price), or hand them a hot drink so they'll feel more warmly toward you. "Expert gardeners know that it doesn't matter how good the seed is unless you've prepared the soil to receive it optimally," Cialdini tells the Journal.
Another important element of executing the technique successfully is to cast only positive roles, as negative ones can hurt both the person and the relationship. A few other helpful altercasting tips the Journal suggests: Know your audience and emphasize your relationship with the person you are casting in a role; be transparent as to why you want him or her to take on a specific role; and use the research-backed word "willing" for large requests, as in, "Are you willing to negotiate the merger contract with me?"