Oisin Prendiville:

Ideally, experiences that users have in one app should stand to benefit them in others. As a community of developers and designers we should be looking to agree upon shared best practices to provide a consistent user experience. There’s an opportunity here to help users understand and embrace drag and drop as a powerful way to interact with touch devices, just as they have on the desktop for years.

This is a great article with video examples on how things work. Oisin recently released Castro 2.5 with his implementation on how it all should work.