Arafah is the name of the Granite hill which is located at the east of Makkah. It is also known as the mount of mercy (Jabal Ar-Rahmah). The hill is the place where the prophet Muhammad (May Allah honour Him and grant Him Peace) stood and delivered the Farewell Sermon to the Muslims who had accompanied him for the Hajj towards the end of his life. ‘Arafah is the most important stop during Hajj, located beyond Muzdalifah.
"During Hajjatul Wadaa' and on the Day of 'Arafah which was a Friday, the Noble ayah was revealed: "Today I have perfected your Deen for you, completed My Favors upon you, and have chosen for you Islam as your Deen." Qur'an.Surah Maidah 5: 3
Allah (Glory be to Him) clearly explains that the Deen for has been perfected, and that it does not require any addition or deletion. That is why Allah (Glory be to Him) sealed Messenger-ship with the Prophet Muhammad (May Allah honour Him and grant Him Peace), being the final and last Messenger. The fact that Allah (Glory be to Him) has chosen Islam as man’s Deen (Way of life prescribed by Islam), means that He does not accept way of life other than Islam from anyone.
Narrated that Yazeed ibn Shaybaan (May Allah have mercy on Him) said: We were standing in ‘Arafah in a place far from the mawqif [where the Prophet (May Allah honour Him and grant Him Peace) stood], Abu Dawood and al Tirmidhi 883. Ibn Mirba’ al-Ansaari (R) came to us and said, “I am the messenger of the Messenger of Allah (May Allah honour Him and grant Him Peace), who says to you: ‘Stay where you are (for it is also the place of standing), for you are standing in the area where your father Ibraheem stood.’” Classed as saheeh by al-Albaani in Saheeh Abi Dawood, 1688.
9th Zilhijjah is called the day of Arafah. It is an important day for the pilgrims.
Then he goes off to 'Arafah and if able stands upon the rocks beneath the Mount of Mercy (Jabal ur-Rahmah) and if not then all of 'Arafah is place of standing.
And he stands facing the Qiblah, raising his hands making du'aa and reciting Talbiyyah.
And he recites much 'La ilaha illAllah ' as it is the best du'aa on the Day of 'Arafah as the Prophet said: The best thing that I and the Prophets have said on the evening of 'Arafah is Laa ilaha illallahu wahdahu laa shareeka lahu lahul mulk wa lahul hamdu wa huwa 'alaa kulli shay'in Qadeer.
And if he adds in the Talbiyyah occasionally (all good is the good of the Hereafter) then that is permissible.
Innamaal Khairu Khairul Aakhirati
And he remains in that state, remembering Allah (Glory be to Him)reciting Talbiyyah, making du'a as he wishes - hoping from Allah that He will make him one of those whom He boasts of (those whom He frees from Fire) to the Angels as occurs in the hadith :"There is no day on which Allah frees more of His slaves from Fire than the Day of 'Arafah, and He verily draws near then boasts of them before the angles, saying :'What do they seek?' "and in another hadith : "Verily Allah boasts of the people of 'Arafah before the people of heaven (the angels), saying : 'Look to my servants who have come to Me dishevelled and dusty.'" and he remains in that state until the sun sets.
If the pilgrim gets tired and wants to have a break by talking to his companions about useful things or by reading from some useful books, especially things that have to do with the generosity and great bounty of Allah (Glory be to Him), in order to increase his hopes on that day, this is good. Then he can go back to beseeching Allah (Glory be to Him)and praying to Him. He should strive to make the most of the end of the day by making du’aa’. The best of dua is dua made on the day of ‘Arafah.
So when the sun has set he leaves 'Arafah for Muzdalifah - going with calmness and tranquility, not jostling or pushing the people with himself or his riding beast or his vehicle, rather whenever he finds room then he goes faster.
And when reaching Muzdalifah he gives adhan and iqaamah then prays the three ra'kahs of Maghrib, then gives iqaamah and prays 'Ishaa - shortening it - and joining the two prayers. And if he separates the two prayers for some necessity then there is no harm in that. And he does not pray anything between them or after 'Ishaa. Then he sleeps until Fajr. Then when the dawn first appears he prays Fajr in the first part of its time with adhan and iqaamah.
When the sun rises, he should proceed to ‘Arafah, and there he should combine the Dhuhr and ‘Asr prayer at the time of Dhuhr, making each one two units. He should remain in the Masjid of Namirah until sunset if possible. He should mention Allah (Glory be to Him) and make as many supplications as possible while facing the Qiblah.
On the day of Arfah after rising of sun, pilgrims should leave Mina to Arafah by reciting Takbeer (Allahu akbar), Tahleel (La ilaha ilal lah), and Talbiyah' There is no greater day than the Arafah day in which a lot of slaves of Allah (Glory be to Him) are released from the hell. (Sahih Al Muslim)
On the day of Arafah,one can keep fast or avoid it, which is optional. The popular statement which forbids fasting on this day is da’ef or zaeef which means it is not authentic (Tirmizi). Before entering Arafah , take rest in Wadi-e-Nimrah listen to the speech (Qutba) of Imam-e-Haj at the time of Zohr and then offer both Zohr and Asar Prayer with one Azaan and two Iqamat along with Jamat with Qasar (by offering Two Rakath) (Sahih Al Muslim)
After offering Zohr and Asar salah, enter in to Arafah and also if possible in the lap of Jabl-e-Rahmat (or) where ever you get place, do waquf (stay) and raising the hands pray Quranic and Nabavi duas and in between also say Takbeer, Tahleel and Talbiyah. (Sahih Al Muslim) and on this day read this dua: Allahu akber Allahu akber laa ilaha illallhu wahdahu laa shareeka lahu lahul mulku walahul hamdu wahuwa ala kulli shaiin Qadeer)(Tirmizi) because it's the Sunnah of Prophets of Allah (Glory be to Him) and our Prophet Mohammed (May Allah honour Him and grant Him peace) and this dua is also authentic. (Innamal kairu kairul Aakhirah), However if the late comers reach the ground of Arafah on 10 Zilhijjah before Fajr even their arfah Rukn is being offered. (Sahih Al Bukhari , Sahih Al Muslim)
After the sunset without offering Maghrib Namaz, leave for Muzdalifa while reciting Talbiyyah with peace and dignity. (Sahih Al Muslim)' It is wrong to imagine or think that the stay at Mina between the 8th and 9th Zilhijjah midnight is compulsory (Fatwa by Mashoor Aal Salman, student of Shaik Albani). 
The Prophet (May Allah honour Him and grant Him Peace) said: The best invocation is that of the Day of Arafah, and the best that anyone can say is what I and the Prophets before me have said: Laa 'ilaaha 'illAllah u wahdahu laa shareeka lahu, lahul-mulku wa lahul-hamdu wa Huwa 'alaa kulli shay'in Qadeer.
None has the right to be worshipped but Allah (Glory be to Him) alone, Who has no partner. His is the dominion and His is the praise, and He is Able to do all things. At-Tirmithi. Al-Albani graded it good in Sahih At-Tirmithi Vol 3:184, and also Silsilatul-'Ahadith As-Sahihah 4/6. 
“Hajj is ‘Arafah” is that in Hajj it is essential to stand in ‘Arafah. Whoever does not stand in ‘Arafah has missed out on Hajj. It does not mean that the one who stands in ‘Arafah no longer has to do any of the actions of Hajj, according to scholarly consensus, because if a person stands in ‘Arafah, he still has to do some actions of Hajj, such as staying overnight in Muzdalifah, tawaaf al-ifaadah, sa‘ee between as-Safa and al-Marwah, stoning the Jamaraat and staying overnight in Mina.