The most common action for an app, the one that needs to be accessed quickly might be added as a bottom edge action, accessed with a swipe from outside of the screen upwards.
You can add a new contact in the Contacts app swiping up:
The hint is used to let the user know that there is something worth trying at the bottom of the screen.
After opening an app, a hint with a text and/or an icon is shown:
After after a few seconds it hides and a floating icon is shown