The word is courtesy:
The courtesy to talk at the right time: "Do you have a moment?"
The courtesy to speak in pleasant tones: slowly, with pauses to give people time to assimilate what you're saying, near the bottom of your pitch range, but when emphasizing a key point, increasing pitch and volume and decreasing speed.
The courtesy to be brief: 10-60 seconds per utterance. That doesn't overwhelm the listener.
The courtesy to ask permission before criticizing: "Would you mind if I offered a suggestion?"
The courtesy to criticize with minimal impact on their self-esteem: "I'm wondering if it might be a good idea to (insert suggestion). What do you think?"
Courteous communication is invaluable to enhancing your credibility and likeability.