This chapter discusses factors that influence the effectiveness of marketing communications and attitude change. It covers principles of persuasion like reciprocity, scarcity, authority, consistency, and liking. When crafting messages, marketers must consider the source, message, and medium. Source credibility and attractiveness impact persuasiveness. Celebrities are often used as sources due to their cultural meanings. The message should be tailored based on factors like vividness and repetition. Interactive communications allow for feedback between marketers and consumers.