Best practices in giving difficult feedback to a leader involve a thoughtful and intentional approach that takes into account both the psychological impact of the feedback and the ultimate goal of improving performance and relationships. Here are key practices based on the provided excerpts:

1. Assess Motivations and Styles: Reflect on the desire to provide feedback and whether it stems from a need for control or discomfort with different working styles. Recognize that diversity in styles is essential for high performance in a complex, interdependent world [9].

2. Invest in Relationships: Build trust and demonstrate care for the recipient's feelings over time. This investment ensures that when feedback is given, it is received within the context of a supportive relationship [9].

3. Timing and Specificity: Choose the right moment to provide feedback, allowing time for emotions to settle while ensuring the details of the behavior are still clear. Be specific about the behavior and the emotional response it triggers [10].

4. Use Supportive Confrontation: Employ the model of "supportive confrontation," which includes explaining the effect of the leader's behavior on you, showing how the behavior doesn't meet their goals, discussing the costs of the behavior, and considering how you might be contributing to the problem [4].

5. Stay on Your Side of the Net: Focus on disclosing your emotional response without making assumptions about the leader's motives or intentions. Use accurate emotional vocabulary to express your feelings [12].

6. Empathy Without Agreement: Understand that empathizing with someone does not equate to agreeing with them. It's possible to comprehend their perspective and emotions without endorsing them [15].

7. Provide Feedback as Data: Treat feedback as valuable information, not a gift, to be used for learning and growth, while filtering out noise or irrelevant information [1].

8. Understand and Mitigate Threat Responses: Be aware of the SCARF model (Status, Certainty, Autonomy, Relatedness, Fairness) and how feedback can trigger social threat responses. Create a psychologically safe environment to reduce these threats [22].

9. Follow-Up and Dialogue: Engage in an ongoing dialogue rather than treating feedback as a one-time event. Consistent follow-up helps normalize feedback and integrate it into the organizational culture [9].

10. Acknowledge Your Influence: Recognize how your behavior and leadership might influence the leader's actions. Taking responsibility can change the conversation from blame to joint problem-solving [27].

11. Model the Behavior You Want: Be candid with feedback and model accountability. Encourage openness about mistakes and setbacks to foster a culture of learning [10].

12. Promote a Team Identity: Avoid creating an environment where fear leads to finger-pointing. Instead, foster a sense of team identity where accountability is balanced with support [14].

13. Engage in Skillful Conversations: When hurt by feedback, engage skillfully by sorting and filtering the feedback, experimenting with new ideas, and discarding what doesn't fit [6].

By applying these best practices, you can deliver difficult feedback to a leader in a manner that is more likely to be constructive and lead to positive change.