Bismillahirrahmanirrahim!
Be nice to people, to your parents and friends, be just and show your friend how it's like to be a good Muslim. If you wake up in the morning to pray, you do it for Allah but people get influenced. When a calamity befalls you, you say "Inna lillahe wa inna ilahi raajioon" these are good qualities that inspire others and they become curious. Remeber you are not doing these things to show off though. Showing off is a major sin. your good deeds should inspire others. Your belief in God and your patience should inspire others.
If one start questioning himself/herself why is he/she walking on this earth, why do we eat drink and talk? why do we have emotions? why do we have sense of good and bad? why are we not like living things? why are we not just 'matter'? Why am I not an animal? what is beyond this planet? what will happen when we die? will we just vanish? Is this world just a mere chance and all these living beings survived here for centuries without vanishing despite so many plagues, so many calamities... If we are here, there must be some one else?
Atheist think that this world came into being by chance and that we came from the matter and they dont know where did the matter come from? Was it here from infinity? They dont know the answer to this question. They say "Nature" made us what if what you call nature is actually God... (Muslims do not believe God and nature are the same ... for the sake of argument and to give him/her a different view on the subject just go on with this, this is more a Hindu concept of God).. so if this Nature can make such an amazing thing like human, how come He cant send you instructions in form of a book or religion... Obviuosly if He can make Human beings, He knows how to communicate with them , communicating with them should be easier than actually making him. Nature is not actually God but it's absurd on their part to think that Nature made you but Nature can not talk or give instructions to you. We believe nature, time and space all came into being because of a Creator.
And who's sustaining the universe? a new calf is born and it knows where it's food is and it will go and suckle on it. There are lots of micro organisms around us but they are not harming us? why? Plagues should have destroyed the entire human population if it wasnt for God who sustained human life on earth. Your body is acting according to a plan, you were just a single cell Zygote and now you are a person who can , talk, walk, laugh, and cry? Why is there love in the earth? If everything was a chance? Is love also a chance thing? why are Lions not eating their children? why are we not killing each other just to satisfy our hunger?
Somebody's watching us, somebody's sustaining this universe; somebody has put the qualities of mercy in our hearts.