These are tasks that tend to have high consequences (e.g., rock climbing or public speaking), clear feedback, and take place in a varied environment.
When you are experiencing flow, it seems like the task at hand is almost performing itself.
But there's still a sense of personal control over it, and working on it feels very rewarding.
We experience the "flow state" when a given task becomes effortless and time slips by without our noticing. It's an absorbing, intrinsically rewarding state that we enter when performing certain tasks.
When in the flow state we experience mindfulness and actions and awareness merge, so that it seems like the task is almost performing itself. Despite this, there's still a sense of personal control over the task at hand, and performing it feels intrinsically rewarding.
Arguably, the most important criteria in the pursuit of flow is to pick intrinsically rewarding tasks that have high consequences (e.g., rock climbing or public speaking), clear feedback, and take place in a rich and varied environment (so not your office cubicle).
... to push your mind beyond its comfort zone. Flow happens when we get a bit out of our comfort zone. Too much, and you get anxious; Too little and you get bored.
You need to know your physical or emotional limitations and consciously push past them.