How to Give Constructive Feedback
Start with a “When you . . .” statement that describes the behavior without judgment, exaggeration, labeling, attribution, or motives. Just state the facts as specifically as possible.
Tell how their behavior affects you. If you need more than a word or two to describe the feeling, it’s probably just some variation of joy, sorrow, anger, or fear.
Now say why you are affected that way. Describe the connection between the facts you observed and the feelings they provoke in you.
From Scholtes, Peter R., The Team Handbook, Joiner Associates (1988)