“These were the maxims of Franklin’s life and those, he believed, most likely to produce good will and lasting friendships.” (Benjamin Franklin’s The Art of Virtue edited by George L. Rogers)
As I thought and researched about the origin of manners I very quickly came to the conclusion that the source of manners is...God, the Creator of all things.  “In the beginning, GOD...”(Genesis 1:1) All that is good, lovely and kind is from Him and is a reflection of His character!  His kindness to us was shown when He gave His only Son to die and pay the price of our sins.  “Greater love has no one than this, that he lay down his life for his friends.”  John 15:13
So what are manners? Here’s a simple definition: “Manners are the outward expression of a person’s inner character.”  The American College Dictionary says that manners are “4. a person’s outward bearing; way of addressing and treating others. 5. ways of behaving, esp. with reference to polite standards.”
As the Lord started to shape Israel, His chosen people, into a godly nation, He gave through Moses general instructions of how they were to conduct their lives.
“Rise in the presence of the aged, show proper respect for the elderly and revere your God.  I am the LORD.”  (Leviticus19:32)  -That was one instruction God gave them.
We don’t have to look too far in Scripture to find the basis for common courtesy and manners.  We are to:

Show proper respect to everyone. (1 Peter 2:17)
Excel in the grace of giving. (2 Corinthians 8:7)
Be kind and compassionate (Ephesians 4:32)
Speak words that build others up (Ephesians 4:29)
Deny ourselves to follow Christ’s example (Luke 9:23-26)
Honor parents and authorities (Ephesians 6:1-3, 5-8)
And so much more!

Where Do We Start?
Following Jesus means following the way of the cross.  We begin with asking ourselves these questions:  “Is my life surrendered to Christ?”  “Am I living a life of self-denial?”  Jesus said: “If anyone would come after me, he must take up his cross daily and follow me.” (Luke 9:23)  As we make good behavior and polite manners a habit, it becomes easier to deny ourselves.  “Come to me, all you who are weary and burdened, and I will give you rest.  Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls.  For my yoke is easy and my burden light.”  (Matthew 11:28-30)
When we deny ourselves we practice self-control, which is also a part of good manners.  Self-control is one of the fruits of the Spirit: “The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control.”  (Galatians 5:22-23)  The Holy Spirit can work His fruits in us, if we just offer a yielded life to Him.  To have genuinely good manners all of the fruits of the Spirit need to be evident in our lives.
Parents might wonder: “how do we start teaching manners to our children?”  Again, first you have to examine your own life and relationship with Christ.  Before your children will learn anything they first must see it demonstrated in your life.  How do you treat your guests, your friends and (most importantly) your family?  Elisabeth Elliot asks: “Are we guilty of treating members of our family in a way we would never dream of treating strangers?  Courtesy is small sacrifices, little ways of saying, ‘My life for yours.’” 
“Do not forget to do good and to share with others, for with such sacrifices God is pleased.”  (Hebrews 13:16)
I think it is also really important to teach your boys to act like gentlemen and your girls to act like ladies.  Here is some advice the Apostle Paul gave to a young man named Timothy: “Do not rebuke an older man harshly, but exhort him as if he were your father.  Treat younger men as brothers, older women as mothers, and younger women as sisters, with absolute purity.”  (I Timothy 5:1-2)
The distinctive lines between men and women have merged and become blurry to most people today.  Clothes, mannerisms and hairstyles are basically the same.  Since the feminist movement the roles of men and women (that were originally given and approved by God) have been reversed.  Women have become the aggressive pursuers.  Most young men brought up today are confused about what their role is, and so they sit back and let the women take charge.  Gone are the days when women were shown protection and care by most men, (i.e., opening doors, taking the heavier load, walking on the side of the street closest to the traffic).  We need to take our children back to the Bible to learn what true men and women are made of.
“I want men everywhere to lift up holy hands in prayer, without anger or disputing.  I also want women to dress modestly, with decency and propriety, not with braided hair or gold or pearls or expensive clothes, but with good deeds, appropriate for women who profess to worship God.”  (I Timothy 2:8-9)

Ambassadors for Christ
“We are therefore Christ’s ambassadors, as though God were making his appeal through us.”  (2 Corinthians 5:20a)
We are ambassadors for Christ.  What we do or how we are dressed reflects our Savior.  We should not copy the ways of the world to look like them.  “Do not love the world or anything in the world.  If anyone loves the world, the love of the Father is not in him.”  (1 John 2:15)
So what message are we bringing to the world through our clothes and actions?  Are we showing forth purity or seductiveness?  Do we have a “look at me” attitude or one real compassion and more concern for others than ourselves?  Do we dress with a look of rebelliousness or slouchiness?  How can we show that we are different if everything about us is just like the world?  To make a difference in this world for Christ we have to be willing to be a little different.  Dress and groom neatly and acting nicely will show something is different.  Then you will attract people’s interest, and they will ask, “why are you so different?”  You have a great opening then for sharing Christ.

Our Speech reflects our heart
Our speech reflects where our heart is as well.  “From out of the abundance of the heart the mouth speaks.”  (Matthew 12:34)  Avoid coarse language or even critical language.  Lift up others.  “Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen…Nor should there be obscenity, foolish talk or coarse joking, which is out of place, but rather thanksgiving.”  (Ephesians 4:29, 5:4)  Always have something uplifting to say.  “If you can’t say anything nice, don’t say anything at all,” is an old adage and is still good advice for today. 

Like Stars in the Universe
How refreshing it is to see a polite young boy who continues to open doors and carry heavy loads for people, in spite of the aggressive feminist movement!
Just a warm smile and a kind word to a harried clerk can make her day and help her to face the complaining, demanding customers.
It makes me excited to think of all the ways and things we can do to become more “winsome” Christians.  With God’s light shining through us into this dark world, many souls can be won for Christ!  Just small gestures of kindness can speak volumes to people burdened with the world’s problems.
“For it is God who works in you to will and to act according to his good purpose.  Do everything without complaining or arguing, so that you may become blameless and pure, children of God without fault in a crooked and depraved generation, in which you shine like stars in the universe as you hold out the word of life…”
Philippians 2:13-16a