The most common mistake Black Belts and Green Belts make is mapping the process as it should work according to the SOP, not as it actually runs on the shop floor. If your as-is map doesn't include the rework loops, workarounds, and informal handoffs that frontline workers actually live with, it won't survive a tollgate review with a Master Black Belt or a skeptical process owner. Whether you're a solo practitioner in a small operation or mapping cross-functional flows across a global plant, agree on your SIPOC scope before you add a single swimlane, and use a consistent notation standard throughout so your map is defensible when finance or quality leadership walks into the room.