Can the Dead See You When You Visit Their Grave?
Question

Is the dead person aware of those who visit him in the graveyard? Is what is required to stand in at the graveside, or is it sufficient just to enter the graveyard? Please advise us, may Allah reward you.
Praise be to Allah.Shaykh `Abd Al-`Aziz ibn Baz (may Allah have mercy on him) said:
“With regard to the dead person being aware of the one who visits him, Allah knows best about that. Some of the early generations said that that is the case, but there is no clear proof for that as far as I know. But the Sunnah is well known; it is prescribed to visit graves and to greet their occupants with Salam, saying: “As-salamu `alaykum dara qawmin mu’minin, wa inna in sha Allahu bikum lahiqun. Nas’al Allaha lana wa lakum Al-`afiyah, yaghfir Allahu lana wa lakum, yarham Allah ul-mustaqdimina minna wa’l-musta’khirin (Peace be upon you, abode of believers, and verily we will, if Allah wills, join you. We ask Allah for well-being for us and for you. May Allah forgive us and you; may Allah have mercy on those who have gone ahead of us and those who come later on).”
All of that is prescribed according to Islamic teachings. 
As for whether the dead person is aware of that or not, this requires clear evidence, and Allah, may He be Glorified and Exalted, knows best. But it does not matter to us whether the dead person is aware of it or not; we have to follow the Sunnah.
It is prescribed and recommended for us to visit graves and to offer supplication for the dead , even if they are not aware of our presence, because this will bring reward to us and will benefit them , because our supplication for them benefits them , and our visit will benefit us too, because it brings reward, and because it is a reminder of death and a reminder of the hereafter, so we benefit from that. And the dead person also benefits from it, because of our supplication for him , and our asking for forgiveness for him, so the dead person will benefit from that.
As for standing at the grave, the matter is broad in scope. If the visitor stands at the graveside, there is nothing wrong with that, and if he stands at the edge of the graveyard and gives the greeting of Salam, that is sufficient. If he stands at the edge of the graves and says: “As-salamu `alaykum ahl ad-diyar min Al-mu’minina wa’l-Muslimin, wa inna in sha Allah bikum lahiqun. Nas’al Allaha lana wa lakum Al-`afiyah. Yarham Allah Al-mustaqdimina minna wa’l-musta’khirin (Peace be upon you, inhabitants of the graves, believers and Muslims, and verily we will, in sha Allah, join you. We ask Allah for well-being for us and for you. May Allah have mercy on those who have gone ahead of us and those who come later on),” that is sufficient, but if he goes to his father’s grave, or if he goes to his brother’s grave, that is better and more proper. 
So if he goes to the grave of his brother, father or relative, or of his friend, and stands by the grave and says “As-salamu `alayka ya fulan wa rahmatullahi wa barakatuhu, ghafara Allahu laka wa rahimaka Allahu wa da`afa hasanatika (Peace be upon you, O so-and-so, and the mercy of Allah and His blessings; may Allah forgave you, and may Allah have mercy on you and multiply the reward of your good deeds),” and the like, that is good, and it is better and more proper.” (Fatawa Nur `Ala Ad-Darb, 1/195)
For more details, please see the following answers: 200530 , 20820 , 13183 , 8198 , and 34361 .
And Allah knows best.