Best practices for scrolling and navigation on touch interfaces: horizontal vs vertical

It's well known that on traditional (mouse/keyboard) interfaces horizontal scrolling goes against user expectations, however in touch devices the matter is not so clear.

Are there any best practices, focused on touch interfaces, to decide whether to use horizontal scrolling or vertical scrolling? Are there any case studies about it?

How can you hint and teach the user which is the navigation style of your app, ie. the way to interact with it? and which ones are the most efficient? (eg. Apple uses pagination dots on the bottom of the home screen but Windows uses the "Panorama", showing a small piece of the following screen)

Does the size/type of device (phone vs tablet) matter for this aspect? For example, even if it's not strictly scrolling, the Flipboard app for iPad uses horizontal pagination or gestures while the iPhone app uses vertical ones.