What Are the Virtues of Surat al-Mulk?
Question

Reading Surat al-Mulk protects a Muslim from the trials of the grave, but how often does one have to read it? Once a day or more?
Praise be to Allah.Virtues of Surat al-Mulk
Abu Hurayrah narrated that the Prophet (peace and blessings of Allah be upon him) said: “A surah from the Quran containing thirty verses will intercede for a man so that he will be forgiven. It is the surah Tabarak Alladhi bi yadihi’l-mulk [i.e.,Surat al-Mulk ].” (Narrated by al-Tirmidhi, 2891; Abu Dawud, 1400; Ibn Majah, 3786. 
Al-Tirmidhi said, this is a sound hadith. It was classed as sahih by Shaykh al-Islam Ibn Taymiyah in Majmu’ al-Fatawa, 22/277, and by Shaykh al-Albani in Sahih Ibn Majah, 3053. 
How often should you recite Surat al-Mulk to get protected from punishment in the grave?
What is meant is that a person should read Surat al-Mulk every night , act in accordance with the rulings contained in it, and believe in the information mentioned in it. 
‘Abd-Allah ibn Mas’ud said: Whoever reads Tabarak alladhi bi yadihi’l-mulk [i.e., Surat al-Mulk ] every night, Allah will protect him from the torment of the grave . At the time of the Messenger of Allah (peace and blessings of Allah be upon him) we used to call it al-mani’ah (that which protects). In the Book of Allah it is a surah which, whoever recites it every night has done very well. (Narrated by al-Nasai, 6/179; classed as hasan by al-Albani in Sahih al-Targhib wa’l-Tarhib, 1475.)
The scholars of the Standing Committee said: 
“On this basis there is the hope that whoever believes in this surah and reads it regularly, seeking the pleasure of Allah, learning the lessons contained in it and acting in accordance with the rulings contained therein, it will intercede for him [in the Hereafter].” (Fatawa al-Lajnah al-Daimah, 4/334, 335)
 And Allah knows best.