To be in a flow state is to be completely present in the moment. Achieving this state creates an endless flow of information from the brain that complements the stimuli in the surrounding environment. So, how is this achieved?
To be able to focus 100% of one’s energy on the goal at hand and not be distracted by anything that comes up on the way to achieving that goal.
Clear the mind and focus on the next step.
Yan's blog 