One footed riding is a base for starting other tricks like Coasting and even Gliding. I way I learnt it was from one foot idling then getting enough momentum and pushing hard on the pedal when it was in front and just doing that once over to one foot idling again till there's enough momentum to go more than one revolution of the wheel. There's the other way which I have seen people learn and that is by riding and when the foot comes to the top of its rev, simply take the foot and put it on the frame which is easier than having the foot dangle. The main suggestion I can tell for this method it to have enough speed but not to much. Here's some variations on one foot riding and also videos of one footed riding.