As for the day of Arafaah:
The Prophet (peace and blessings of Allaah be upon him) said: “There is no day on which Allaah frees more people from the Fire than the Day of ‘Arafaah. He comes close and expresses His pride to the angels, saying, ‘What do these people want?’”
As for fasting on the day of Arafaah for those not performing Hajj:
The Messenger of Allaah (peace and blessings of Allaah be upon him) was asked about fasting on the Day of ‘Arafaah. He said, “It expiates for the sins of the previous year and of the coming year.” Narrated by Muslim.
As for the du’aa of the fasting person:
Our Prophet (peace and blessings of Allaah be upon him) said: “There are three prayers that are not rejected: the prayer of a father for his child, the prayer of the fasting person and the prayer of the traveller.”
As for Du’aa in sa’at al-Istijabah on Friday:
Jâbir (may Allah be pleased with him) relates that the Prophet Sall Allahu ‘alayhi wa sallam said: “Friday is comprised of twelve hours. There is one in which a Muslim who asks Allah for something will have it granted to him. Seek it in the last hour after `Asr.”
My dear brothers and sisters, Allah alone knows whether we will ever get this opportunity again or not. Prepare for it from now. Make a list of du’aas you want to make and spend the final hour before Maghrib this coming Friday sincerely pleading to Allah. This IS one of THE best opportunities we may get for a while.