Q: Is it recommended to make tabkir during the 10 days of Dhul-Hijjah?
A: The unrestricted takbir (al-Takbir al-Mutlaq) begins at the commencement of Dhul-Hijjah and concludes at the end of the Eid khutbah on the Day of Sacrifice (Yawm al-Nahr).
This takbir is made at any time and in any place in which dhikr is permitted and is not associated with the obligatory congregational prayers like the restricted takbir (al-Takbir al-Muqayyad).
The takbir is as follows, Allahu Akbar, Allahu Akbar, la illaha illa Allah, wa-Allahu akbar, Allahu akbar, wa lillahil-hamd.
Source: Kashshaf al-Qina'