Muhammad salallahu alleyhi Salam taught us perfect manners and he said 'The best amongst you are those who have the best manners and character.' Al-Bukhari
One characteristic that we see commonly today amongst people is lying, lies come so freely
to the tongues of people, for a Muslim this is a serious sin.
Even in everyday matters we have to avoid falsehood and lying, for example a mother was calling her child by enticing him that she will give him something if he came when she called him, the Prophet salallahu alleyhi wa salam, was there and he warned her that if she wouldnt give it to him, then she would be a liar.