This is recommended for those 10 days

To pronounce the reminder formulas: Takbir: “
Allahu Akbar"
Tahlîl: "La Ilahha Illallah"

 Tahmid: "Al-Hamdu Lilah"

 For according to the hadith of Ibn 'Umar (radha Allahu anhu), the Prophet (sallallahu alayhi wa sallam) said: " There are no more important days with Allah - exalted be He - and Of which the works are more loved by Him than during these ten days. So in this period, repeat formulas "Allahu Akbar", "La ilaha illa'Llah", "Al-Hamdu Lilah " (At-Tabarani in Al-Kabir Mu'jam ul.)
Fasting: some wives of the Prophet reported:”the Prophet fasted 9 (first) day of Dhul-Hijjah, the day of Ashura, and three days a month. ” (Ahmad, Abu Dawud and Al-Nasa'i.)
 The fast of the Day of Arafat (9th day of Dhu'l-Hijjah): fasting this day is aSunnah confirmed for those who do not perform Pilgrimage, according to the hadith of the Prophet (sallallahu alayhi wa sallam):”I hope for the reward of Allah that this fast erases your sins of the past year and those of the year to come. " (Muslim)
The Hajj and Umrah:

 Abu Hurairah (Allah Allâhou anhu) reported the Prophet (sallallahu alayhi wa sallam) that he said: " Fulfilling the Umrah away the sins between this' Umrah and The last, and an accepted Hajj (of Allah) has no other reward than paradise.”