As we know, any human being's body contains flesh, blood, and bones. And they feel tired, and everyday they are born and they die. And mankind is always helpless, if one breath stops, then the second breath will never be acquired.  

Lets realize what shirk actually is, it is to bring the status of the creator to the status of the creations. Which is represented by the verses in the Qur'an:

Say (O Muhammad (Peace be upon him)): "He is Allâh, (the) One. (112:1) 

It is an open challenge to mankind that no one is worth of worshipping accept Allah. Why? Because all human beings might be stronger than each other, however they all feel tired, eat, and sleep. And if anyone claims to be close to the power of Allah, then who can be? Because Allah never feels fatigued, why? Because if He is sleeps, then all of the planets in the universe orbiting in a balance, will be destroyed. And this is why Allah says "Say (O Muhammad (Peace be upon him)): "He is Allâh, (the) One. " 

If any individual associates partners with Allah, and mixes with Allah's bounty, then he is misguided. And this is to associate partners with Allah. Regardless Muslim or non-Muslim. If a non-Muslim does it, it is because he or she is not educated about Allah. But if one who claims to be a Muslim, if asks from any apostle (peer) or is going to dead people in there graves, and asking help from them, or through them, then they are associating partners with Allah (Shirk).

 
"Allâh-us-Samad (The Self-Sufficient Master, Whom all creatures need, He neither eats nor drinks). (112:2)

Allah is a power who does not depend on anything, and is not waiting for anyone's help to help him run his universe. And everything seeks help from Allah only, regardless how pious someone may be, even if it is the Prophet Muhammed , or Moses (Musa), or Jesus (Isa), or any other Prophet. These were all human beings, and they came to give message to mankind. And the Prophet Muhammed was the last and final Prophet, and is the one who left revelation for all of mankind, and left behind the Qur'an and the hadeeth (examples of the Prophet )

"He begets not, nor was He begotten. (112:3)

The verse above certifies to us that the status of the creation is not comparable to the status of Allah. A mother gets pregnant, and the fetus develops in her womb, and after delivery, it is from the most unpure section. And how much does the baby depend on the mother? So how can Jesus or anyone else come close to the status of Allah. If Jesus was god, then why was he born from his mother Mary, and why as a baby depended on his mother.

So any peer or any other human being are all depending on Allah. And there growth, and life is in the hands of Allah. So any creation can never mix with Allah at all.

"And there is none co-equal or comparable unto Him." (112:4)

You (Alone) we worship, and You (Alone) we ask for help (for each and everything). (1:5)

There are many verses found in the Holy Qur'an, which clears the mind of an individual, reffering to no other human being which can help, except for Allah. Whoever is seeks help from others, other than Allah, should stop immediately, because this is a great form of Shirk (associating partners with Allah).

And truly you have come unto Us alone (without wealth, companions or anything else) as We created you the first time. You have left behind you all that which We had bestowed on you. We see not with you your intercessors whom you claimed to be partners with Allâh. Now all relations between you and them have been cut off, and all that you used to claim has vanished from you. (6:94)