All babies cry. It is not necessary to prove. Whatever angel was not your child, sooner or later something is not like it — and Oh how the siren howl.
If they are different parents respond differently to their crying babies: some from melt is allowed and hardly do not start to cry out of pity, others begin to shout, scold and beat. And how to react properly?
To get started you just need calm, gentle but confident voice to ask what happened. It may well be that your child just hungry, or tired, or something hurts, and tears — this is the single most effective way to attract the attention of parents, as the verbal system is not yet very developed.
But it is important to ask "what happened?" an adult in a serious tone (not angry), without lisping and aggression.
If the child is crying because he wants you to buy him some unnecessary trinket to give is not necessary. But if you have no joy and have tools still treat the child. In any case, hug yourself, take pen and kiss. Sometimes it works better than even the coolest toy.
Nothing explains the crying baby if he's hysterical. Better try to distract him and reassure show me the book, movie, something interesting on the street, I topic to something else.
Only when he calms down, serious talk with him, find out all the reasons, explain that crying is not the way out.