وَهُدُوا إِلَى الطَّيِّبِ مِنَ الْقَوْلِ وَهُدُوا إِلَى صِرَاطِ الْحَمِيدِ
"And they have been guided to the purest of talk; and guided to the path of Him who is worthy of praise (22:24)
When one speaks, one should speak only what befits a situation and be brief in doing so. If one is amongst the youngest present, you should not speak unless you are asked to, or you know that your talk will be well received, will benefit or please others. One should not prolong speech, but be clear, concise and to the point rather than prolonging on and on.
Anas (رضى الله عنه) reported;
"The Prophet's (صلى الله عليه وسلم) speech was clear and succinct, neither too long nor too short, and he disliked chattering and ranting." (Sahih Bukhari)
Similarly it was reported in Bukhari and Muslim that 'Aisha (رضى الله عنها) said,
"The Prophet (صلى الله عليه وسلم) spoke [so few words] that you could count his words."
If you hear the athān, stop talking, listen to it and respond to the call of Allāh. Many people, even those with Islamic knowledge, continue talking while the athān is being called. This is rude, as those hearing the athān should listen to it and quit speech, study and even the recitation of the Qurān. Thoughtfully, one should reflect on the words of the athān and the meaning of the call, and one should stop doing all other things, such as speech, study or recitation of the Quran even.
Speech, and the adab of conversation reflects one's personality. It is speech and the actions of the tongue that may lead a person to the hellfire. The tongue is the best and most delicate muscle, for it can benefit and harm. The wise one is He who thinks before speaking. This not only involves the tone, the topic of conversation, the benefit of our speech and the adāb and ettiquettes of listening and debating, but encompasses also one's intention. When one speaks, the tongue should not just flow mindlessly, but one should think about the consequence first.