Gamasutra recently posted a feature/interview with lead Social Designer Aki Jarvinen of Digital Chocolate, highlighting the need for social games to grab people early. How early? Well Jarvinen believes that if you haven’t captivated the potential user within the first 5 minutes of the game, then you’re probably not going to go too far. 

Jarvinen stated that this was "Because players of social games do not fork out money to have the chance to try out a game, their time is of precious quantity. Therefore developers need to catch and hold their attention both through viral spread and gameplay itself.”

The article continues on to provide some ideas on how to help game developers with snagging the consumer’s interest as early in as possible. Someone grabbed within the first five minutes of a game is more likely to continue to play the game, as well as helping the game to go viral. The process of hooking a gamer within that first crucial window is a process called that Jarvinen calls “onboarding” which has three steps: accommodate, assimilate, and accelerate. 

"In terms of games, accommodation is about giving the necessary tools to the player, i.e. the necessary game mechanics and resources to start with. Assimilation gains a specific meaning from the context of the social network: It accounts for assimilation into the progress of one's friends playing the game, and the benefits from playing parallel to your friends. Acceleration then is about getting the player to engage with the game's full feature set and its possibilities."

You can check out the full article here. It will walk you through the first five minutes of several web-based games that have done pretty well for themselves. It can help you get an idea of what people are looking for, and how to include it in your game.