Memorizing Quran and the virtue of some soorahs
Question

Can you please state some of the benefits of reading the following Soorahs with references to Hadith. 
Soorah Naba , Soorah Al-Waqiah , Soorah Yaseen , Soorah Mulk
I am in my mid-thirties and am trying to memorize the Quran as much as possible. Which Soorahs should I start with? and is it okay to recite the part learnt in Nafil Salaat. What should I do if I make a mistake while reciting or forget after reciting several ayahs.
Praise be to Allah.Firstly: 
With regard to the virtues of Soorat al-Naba’ and the reward for reading it, we do not know of anything that applies specifically to this soorah apart for what is known about the rest of the Quran; there is nothing special about this soorah as it were, apart from what we know that whoever reads one letter of the Quran will have one good deed is recorded for him. ‘Abd-Allah ibn Mas’ood said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever reads one letter from the Book of Allah will earn one good (hasanah) thereby. One good deed is equal to ten good deeds the like of it. I do not say that Alif-Lam-Mim is a letter, but Alif is a letter, Laam is a letter and Meem is a letter.’” 
Narrated by al-Tirmidhi, 2910; classed as saheeh by al-Albaani in Saheeh al-Tirmidhi, 2327 
But it was narrated that it is one of the soorahs containing warnings that were very difficult for the Messenger of Allah (peace and blessings of Allah be upon him). 
It was narrated from Ibn ‘Abbaas that the Prophet (peace and blessings of Allah be upon him) said: “Hood, al-Waaqi’ah, al-Mursalaat, ‘Amma yatsaa’iloon [al-Naba’] and Idha al-‘shamsu kuwwirat [al-Takweer] have made my hair grey.”
(Narrated by al-Tirmidhi, 3297. classed as saheeh by Shaykh al-Albaani, al-Saheehah, 955) 
With regard to the virtues of Soorat al-Waaqi’ah, there is a hadeeth which speaks of its virtues, but that hadeeth is not saheeh. 
It was narrated from Shujaa’ from Abi Faatimah that ‘Uthmaan ibn ‘Affaan (may Allah be pleased with him) visited Ibn Mas’ood when he was sick. He said, “What is hurting?” He said, “My sins.” He said, “What do you need?” He said, “The mercy of my Lord.” He said, “Shall we not call the doctor for you?” He said, “The doctor made me ill.” He said, “Shall I order that your regular income [from the state] be restored to you?” He said, “You did not let me have it before today and I have no need of it now.” He said, ‘Then leave it to your family and dependents.” He said, “I have taught them something which, if they say it, they will never become poor. I heard the Messenger of Allah (peace and blessings of Allah be upon him) say, ‘Whoever recites al-Waaqi’ah every night will never become poor.” 
(Narrated by al-Bayhaqi in Shu’ab al-Eemaan, 2/491. This hadeeth was classed as da’eef by Shaykh al-Albaani in al-Silsilah al-Da’eefah, 289). 
With regard to the virtues of Soorah Ya-Seen, there are ahaadeeth concerning its virtues which are not saheeh. 
It was narrated that Anas said: “The Prophet (peace and blessings of Allah be upon him) said: ‘Everything has a heart and the heart of the Quran is Ya-Seen. Whoever recites Ya-Seen, Allah will record for him the reward of reading the Quran ten times.’” 
(Narrated by al-Tirmidhi, 2887. He said, It is not saheeh because of its isnaad, and its isnaad is da’eef (weak). Al-Albaani said in al-Da’eefah (169): (it is) mawdoo’ (fabricated)). 
The same applies to the hadeeth narrated from Abu Hurayrah, which says that the Messenger of Allah (peace and blessings of Allah be upon him) said:  “Allah recited Ta-Ha and Ya-Seen one thousand years before He created the heavens and the earth. When the angels heard the Quran they said, ‘Glad tidings to the nation to whom this will be revealed, and glad tidings to the hearts that will bear this, and glad tidings to the tongues that will speak these words.’” 
(Narrated by al-Daarimi, 3280. al-Albaani said in al-Da’eefah (1248): (it is) munkar (a form of da’eef or weak hadeeth)). 
And the same may be said of the hadeeth narrated from Ma’qal ibn Yassaar, which says: The Prophet (peace and blessings of Allah be upon him) said: “Recite Ya-Seen over your dead.” 
(Narrated by Abu Dawood, 3121; Ibn Maajah, 1448. Shaykh al-Albaani said: With regard to reciting Soorat Ya-Seen over the deceased and turning him to face the qiblah, there is no saheeh hadeeth to this effect. Ahkaam al-Janaa’iz, p. 11) 
And the same may be said of the hadeeth of Anas ibn Maalik according to which the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever enters the graveyard and recites Soorat Yaa-Seen, (the torment) will be reduced for them that day, and he will have hasanaat equivalent to the number of people in the graveyard.” 
Shaykh al-Albaani said in al-Da’eefah (1246): It is mawdoo’ (fabricated). It was narrated by al-Tha’labi in his Tafseer (3/161/2) 
With regard to Soorat al-Mulk, there are saheeh ahaadeeth which speak of its virtues: 
It was narrated from Abu Hurayrah that the Prophet (peace and blessings of Allah be upon him) said: “There is a soorah of the Quran containing thirty verses which have interceded for a man until he was forgiven. It is the soorah Tabaarak alladhi bi yadihi’l-mulk.” 
Narrated by al-Tirmidhi, 2891; Ahmad, 7634; Abu Dawood, 1400; Ibn Maajah, 3786. This hadeeth was classed as hasan by al-Tirmidhi and by al-Albaani in Saheeh al-Tirmidhi, 3/6. 
Another hadeeth which speaks of its virtues was narrated from Jaabir, that the Prophet (peace and blessings of Allah be upon him) never used to sleep until he had recited Alif-laam-meem tanzeel [al-Sajdah] and Tabaarak alladhi bi yadihi’l-mulk [al-Mulk]. 
Narrated by al-Tirmidhi, 2892; Ahmad, 14249. Al-Albaani said in Saheeh al-Tirmidhi (3/6) that this hadeeth is saheeh. 
Secondly: 
There is no set way to memorize Quran. People vary in their ability to commit things to memory; each person has a way and a time that suits him. 
Some people like to read and memorize after Fajr prayer; some like to do so after Maghrib. So look at your own situation and do what is best for you.  
Some people find the short Makkan soorahs easier, and some find the long Madeenan soorahs easier, so start with whichever is easier for you. 
You could start with the soorahs which are often heard and are easy to memorize, such as al-Kahf and Maryam, and the later juz’ (parts) of the Quran. This will give you a motive to complete your memorization, when you find that you have memorized many juz’. 
One of the most important means of consolidating what you have memorized and not forgetting it is to repeat it and go back to it all the time. Some people who have tried to memorize the Quran recite it as they walk in the street and when riding buses, when going into shops and marketplaces, and in all circumstances and at all times, night and day. 
Acting upon what you have learned of the verses of Allah is one of the best means of memorizing the Quran by heart.  
It was narrated that Abu ‘Abd al-Rahmaan said: The companions of the Prophet (peace and blessings of Allah be upon him) who used to teach us Quran told us that they would learn ten verses, then they would not move on to the next ten verses until they had learned the knowledge contained therein and how to act upon it. They said, So we learned the knowledge and how to put it into practice. 
Ahmad, 22384 
What is well known and has been tried and tested by people is that the best way to memorize Quran is to repeat it in prayers such as Sunnah and naafil prayers, etc – or in the fard prayers for the imam } – especially in Qiyaam al-Layl (naafil prayers at night). There is nothing wrong with reciting the juz’ which you are learning in naafil prayers. 
But if you forget some part of the Quran when you are praying, try to remember it until you feel that you will not be able to remember it, then there is nothing wrong with moving on from the part that you cannot remember, to the following part that you can remember. When you finish you prayer, go to the Mus-haf and review the part that you had forgotten.  
And Allah knows best.