1) The sun does not rise on any days greater than the ten of Dhul Hijjah. Actions in them are magnified, the best are: Prayers, Takbeer, Charity, Fasting, and Hajj. In virtuous times, sins are also magnified.
2) The ten days of Dhul Hijjah are the best days of the year while the last ten nights of Ramadan are the best nights. Whosoever has been enabled [by Allah] to pray in the days of the former and the nights of the latter, then he is the successful one.
3) In the ten days of Dhul Hijjah, Allah spoke to Musa (A.S), Islam was completed in it, and Allah made an oath by them. Worship in them is greater than any other day especially Takbeer and Fasting - and Arafah is the best day of the year.
4) The most authentic form of Takbeer is: Allahu Akbar, Allahu Akbar, Allahu Akbar Kabeera... Salman Al-Farisi (R.A) used to encourage people to say this. (Narrated by Abdur Razzaq with an authentic chain).
5) It is recommended to make up the missed fasts of Ramadan in the ten days of Dhul Hijjah to seek the rewards of the missed fasts and fasting the ten days. Omar (R.A) said: (No days are more beloved to me to make up Ramadan fasts than these ten days.)