From the Fajr of 9th Dhul Hijjah to the ‘Asr of 13th Dhul Hijjah, after every Salaat, every Muslim man and woman should recite Takbeer Tashreeq. As mentioned in Fatawa A’alamgiri:
(Fatawa A’alamgiri, Vol. 1, Pg. No. 152)
To say the Takbeer Tashreeq once is Wajib (compulsory) and saying it thrice is better (Afdhal). The Takbeer Tashreeq is this:
Transliteration of Dua: Allahu Akbar Allahu Akbar La Ilaha Illallahu Wallahu Akbar Allahu Akbar Wa Lillahil Hamd.
Muslims should also fast in the first 9 days of Dhul Hijjah. At the very least, one should fast on 9th Dhul Hijjah, which is recommended by the Sunnah and has much excellence.
Thus, there is a Hadith in Sahih Muslim:
Fasting 3 days of every (Islamic) month, fasting in one Ramadhan after the last one has reward of fasting for the whole life. By fasting on the day of ‘Arafah (9th Dhul Hijjah), I hope that Allah Most High will forgive the sins of the year prior to it and the year following it. I hope that by fasting on the 10th of Muharram, Allah Most High will forgive the sins of the year gone by.
(Sahih Muslim, Hadith No. 2803)