3D Touch has significantly improved the way you can interact with an iPhone and while it’s currently available only on the iPhone 6s and 6s Plus, you can expect it to become the norm for all future iPhone models (at least until something even better comes up).
Among the many useful things you can do with 3D Touch, there’s a quick way to access the multitasking app switcher. Sure, the classic shortcut (double-pressing the Home button) is not that bad, but using 3D Touch can surely make opening the multitasking app switcher faster, once you get the hang of it.
To use this trick you’ll need a 3D Touch-enabled device, and right now this means either the iPhone 6s or 6s Plus. Until you learn how this works, it’s recommended you practice with your iPhone on a fixed surface such as a table or a desk (I promise it’s not that hard as it sounds).
Force touch the left edge of the screen (as close to the edge as possible). The pressure you need to apply depends on how you configured the 3D Touch pressure settings.
Slowly swipe to the right while still pressing until you see the App Switcher multitasking screen then let go to view it in full size. This it the exact result as double-clicking on the Home button.
Alternatively, if you hard press the left side of the display, keep pressing and then swipe to the right all the way, this will take you back to the previous app.
To be honest, both the 3D Touch method and the old one using the Home button to bring up the app switcher are probably just as fast. However, which one each of us decides to use is obviously a matter of personal preference.