When reprimanding a difficult person, as in all your dealings with employees, you must be careful to preserve the person's dignity. Here are some basic guidelines to follow:
1. Do focus on the problem.
2. Don't attack the individual personally - stick to the undesirable behavior.
3. Do make sure that your position is supported by human resources or your superiors.
4. Do document everything you do.
5. Don't confuse your employee by sending mixed or conflicting messages about his performance.