Step 1: Understand the leadership styles.
Effective leaders often use tact, diplomacy, and persuasion to guide their subordinates towards achieving goals.
Step 2: Evaluate the options.
- Tact involves handling sensitive situations with care, a key skill for any effective leader.
- Using a "rod" or "threatening" approach can lead to negative outcomes, such as low morale and resistance.
- "None of these" is incorrect because leadership involves guiding and motivating subordinates in a positive manner.
Step 3: Conclude.
Leaders must rely on tact to gain cooperation and foster a positive working environment.
Final Answer:
\[
\boxed{\text{By tact}}
\]