Images sell better than words
When user review which app to download, they first look at the app icon and screenshots to get a feel for what the app does and how it looks. That’s why creating self explanatory screenshots is key to increase downloads.
Screenshots can be created easily from the devices or simulators but for many applications, showing what it’s the app is not enough. That’s why many apps have app benefits added on top of the screenshots or show real people interacting with the app.
Creating nice screenshots with mobile devices like iPhone, Android phones on them doesn’t have to be hard. Below is a Youtube video I created where I demo how to use 2 web tools (http://www.mockuphone.com and http://www.placeit.net) to create this kind of screenshots.