Bucket groups of employees evenly into 3 bins (think "top", "middle", "bottom"), then split those into 3 bins each to arrive at 9 bins of employees. Then assign ratings to the bins. Note: Some teams choose different "axes" for the bins ー e.g. primary bins representing performance, and then the secondary bins representing potential.
9 Bin Step 1: Group Employees into 3 Primary Bins
9-Bin Step 2: Split further into 3 Secondary Bins
9-Bin Step 3: Assign Ratings and Comments by Bin