To communicate your required behavioral changes, a six part message format can be used. It is designed to get the employees attention, to focus on their behavior, and inform them of the consequences for failure to change.
Describe how their behavior affects the group.
Describe how their behavior affects the coworker who is the recipient of their behavior (if appropriate).
Describe how you feel about their behavior.
Describe your future performance expectations.
Describe the sanctions for failure to change.
And of course, DOCUMENT the conversation and have the employee agree on the behavior changes.
~ This is an excerpt from Working With Difficult Employee Problems, a Mastering Leadership Skills seminar.