This video talks about the four quadrants of the base and which should be used for rounding the base. When rounding the base, the runner should hit the front inside corner and use the base as a push off point to accelerate the runner toward the next base.
The player should make the tightest turn possible when rounding the base and each player will have different optimum turns and distances they need to swing out. The key to the turn is that you want a straight line from first base to second base.
Make sure the turn is in stride when touching the base and don’t be concerned about which foot hits the base as long as the player don’t lose momentum going toward the next base. The ending of the video shows techniques on how to make a tighter base turn.