Capturing screenshots of your app for iTunes Connect can feel like a laborious process. For clients that don’t have a Mac, I have to advise them to take manual screenshots on their device using the sleep and home button combination and then to email it to themselves. However, this is really slow, and should be done only if you do not have a Mac.
 
If you do have a Mac and you’ve installed XCode, then it’s relatively painless to do screen captures. And no, I don’t advise buying an app or some other method to do this.
 
1. Launch XCode and open up your XCode project file.
2. Build and run your app on the iPhone Simulator (or the iPad Simulator).
3. Simply press Cmd+Ctrl+C.
4. Launch the Preview app, and create a new file from the Clipboard.
5. Your screenshot is now available to be saved as a png file. (I recommend removing the 20px status bar by cropping it from Photoshop or some other image-editing tool.)
 
That’s it!
 
PS. Others recommend just using the default OSX method for screen captures, but I don’t recommend it due to the fact that it’s hard to get the pixel sizes right.