Praise be to Allah, The Almighty, Who created man with intelligence. He gave us souls and knowledge, as we are developing educationally in order to become characterized by the best of morals and refrain from evil doings.

Manners, it is a way of act, do, behave in prevailing customs, social conduct, and norms of a specific society, period, or group in society. According to Wikipedia, manners, in sociology, are the unenforced standards of conduct which demonstrate that a person is proper, caring, non-grouchy, polite, and refined. They are like laws in that they codify or set a standard for human behavior, but they are unlike laws in that there is no formal system for punishing transgressions, the main informal "punishment" being social disapproval. They are a kind of norm. What is considered "mannerly" is highly susceptible to change with time, geographical location, social stratum, occasion, and other factors.

So, what is the relation between Islam and manners? Islam teach manners, because it is another mission of Rasulullah (صلى الله عليه وسلم) to perfect the manners of the people, as mentioned in one hadeeth "I have been sent only for the purpose of perfecting good morals." (Bukhari). Furthermore, Islam may not be spread to places like Indonesia, Malaysia, Gambia, North Europe, etc. if it was not due to the manners of the Muslim merchants who travelled there for trading.

It is very sad, that nowadays, as we notice that many of us, our family, brothers, sisters, neighbors, youngsters, somehow forgot or simply became ignorance about the importance of manners in the society. How does this happened? Because we are not following the Quran and the Sunnah (the path of Rasulullah (صلى الله عليه وسلم)). Manners is important as it is a key factor for a nation to prosper.

Some of the manners Rasulullah (صلى الله عليه وسلم) has taught us in some hadeeth
* Making peace among people: "Doing justice between two men is charity, and assisting a man to ride an animal or to load his luggage on it is charity; and a good word is charity, every step which one takes towards the mosque is charity, and removing harmful things from the way is charity." [Bukhari]

* Kindness to ones wife: “You will never spend anything seeking thereby the Face of Allah, but you will be rewarded for it, even (the food) that you put in your wife’s mouth."[Bukhari 56]

* Being good to neighbors: "By Allah, he is not a believer! By Allah, he is not a believer! By Allah, he is not a believer." It was asked, "Who is that, O Messenger of Allah?" He said, "One whose neighbor does not feel safe from his evil." [Bukhari].

* Guarding Secrets: "The most evil of the people to Allah on the Day of Resurrection will be the man who consorts with his wife and then publicizes her secret." [Muslim]

* Politeness in Speech: "It is also a charity to utter a good word." [Bukhari]

* Honoring the Guest & kin’s: "He who believes in Allah and the Last Day, let him show hospitality to his guest; and he who believes in Allah and the Last Day, let him maintain good relation with kin's; and he who believes in Allah and the Last Day, let him speak good or remain silent." [Bukhari]

* Being Generous to all creatures: "No Muslim plants a tree or crop, and its fruit is eaten by birds, people or animals, except that it will be regarded as charity for him." (Bukhari)

Then how can we prevent ourselves from doing bad manners?
Allah clearly told us in Quran

إِنَّ ٱلصَّلاَةَ تَنْهَىٰ عَنِ ٱلْفَحْشَآءِ وَٱلْمُنْكَرِ
"And establish regular Prayer: for Prayer restrains from shameful and unjust deeds" [29:45]

خُذْ مِنْ أَمْوَالِهِمْ صَدَقَةً تُطَهِّرُهُمْ وَتُزَكِّيهِمْ بِهَا
"Take, [O, Muhammad], from their wealth a charity by which you purify them and cause them increase, and invoke [Allah 's blessings] upon them " [9:103]

which means that prayer and charity will help and protect us from doing bad.

Good manners can be achieved by teaching ourselves such as the following points:

1. Following in the footsteps and copying the examples of the Messenger of Allah, his infallible household (Ahlul Bayt) and the most righteous among his companions. Studying their biographies and considering all aspects of their virtuous behavior are essential ways of being led on the right path.
2. Practice makes perfect and we should practice conducting ourselves with the best of morals, like truth, courage, generosity, mercy, benevolence and forgiveness. Whoever repeatedly does good deeds and behaves in a principled manner, such conduct will undoubtedly become habitual, whereas whoever commits misdeeds and ill-natured vices like hypocrisy, lying, deceiving ...etc. will accept them to such an extent that they will not feel their abomination and the damage they cause.
3. Avoiding people characterized by bad manners and not making them friends, because not mixing with such people removes the danger of being misled and should also discourage their unprincipled behavior.
4. Accept criticism and work on improving.
5. We should also ask the forgiveness of Allah in case of committing sins or doing evil deeds and should regret and repent for such actions. This can be done through reprimanding ourselves and feeling that such action is bad and should not be repeated.

Good manners surely indicate the goodness of the upright human soul. A good human soul is like a sweet flower from which fragrant perfume is emitted. The man with good morals is considered the foundation on which the structure of a sound Islamic society is built, and is among the causes of giving strength to Muslims. Allah bids us towards the best morals and will reward us accordingly on the Resurrection Day and also forbids us against bad morals for which He will duly punish us. The onus is on all Muslims to ensure good morals which are preserved by way of self-education and practicing exemplary behavior.

May Allah almighty give us all the ability to practice upon the Sunnah and teachings of Rasulallah (صلى الله عليه وسلم).

http://www.islam.org.hk/ECOI_2012/en/Manner_in_Islam/MannersinIslam.htm
https://www.al-islam.org/the-characteristics-of-a-muslim-al-balagh/practising-good-manners
https://haqislam.org/articles/islamic-manners/