Turning Left after Crossing 1B

[bwbuddy]

I assume the answer to this question is the same in all "diamond" sports, but I saw an NSA 12U fastpitch team called out 4 times in a game last night for this same violation, so:

What's the best way to judge whether or not the batter-runner "attempts" or "turns toward" 2B after crossing 1B, and is therefore subject to be tagged out? I realize it has to be more than just simply turning left to return to 1B, but what do you watch for to determine "jeopardy" -- one step towards 2B, two steps, or something else?