Search is the default if Vlingo does not recognize a command in what you said. On the Home screen, for best results, say specifically what you want to do.
On the other Apps in Vlingo, you do not need to specify what you want to do. On the Home screen, you will see examples of comands that you can issue to Vlingo. If you tap on the examples, Vlingo will bring up the What Can I Say? page with the full list of examples.