Successful games manipulate people, creating artificial tasks and challenges that people love to spend time on. This is hard but one can learn it. Hard it is because one need to carefully balance difficulty. A game must pose a challenge to be interesting but avoid being too hard and thus frustrating. Guess why so many games come with some concept of levels of difficulty?
The learnable part is game mechanics. Game mechanics is about the building blocks of a game, design patterns for artificial tasks and challenges that engage the player. The SCVNGR Game Dynamics Playdeck documents 47 such patterns. Their use is not limited to recreational games. Applications and Web sites may employ some of the elements, and con artists and social engineers are exploiting some very similar strategies to trick people into compliance.