Uthman (R.A.) states that a person who recites from
إِنَّ فِي خَلْقِ السَّمَاوَاتِ وَالْأَرْضِ
in Surah Al-Imran till the end of the Surah on any night or part of the night, will receive the reward of performing his Salaat for the whole night.
Jabir (R.A.) states that Prophet Mohammad (S.A.W.) never slept before reciting Surah Alif Laam Meem Sajda (21 para) and Surah Tabarakal Lazi.
Abdullah bin Masood (R.A.) narrates that Prophet Mohammad (S.A.W.) has stated that the person who recites the last two ayats of Suratul Baqarah till the end, then these two ayats will be sufficient for him, i.e. Allah will protect him from all evil and ploys.
When retiring to sleep, make wudhu, dust off the bed three times, lie on the right side, place the right hand under the head or cheeks and recite the following dua three times.
(Mishkat and Hsinul Hasin, Bukhari Muslim)
اللَّهُمَّ قِنِي عَذَابَكَ يَوْمَ تَجْمَعُ عِبَادَكَ
"O Allah, save me from the punishment on the Day when You will gather Your servants".
Alternatively recite this dua
بِاسْمِكَ رَبِّي وَضَعْتُ جَنْبِي وَبِكَ أَرْفَعُهُ إِنْ أَمْسَكْتَ نَفْسِي فَارْحَمْهَا وَإِنْ أَرْسَلْتَهَا فَاحْفَظْهَا بِمَا تَحْفَظُ بِهِ عِبَادَكَ الصَّالِحِينَ
"Oh my Lord, I have taken Your name and placed myself on my side and by Your power will rise up again. If you take my soul whilst I am sleeping (grant me death) then have mercy on my soul and if you leave me (let me live) by your power protect me by that with which you have protected your righteous servants".
Or recite this dua
اللَّهُمَّ بِاسْمِكَ أَمُوتُ وَأَحْيَا
"O Allah, by Your name I live and die".
Or recite this dua
اللَّهُمَّ أَسْلَمْتُ نَفْسِي إِلَيْكَ وَوَجَّهْتُ وَجْهِي إِلَيْكَوَفَوَّضْتُ أَمْرِي إِلَيْكَ وَأَلْجَأْتُ ظَهْرِي إِلَيْكَ رَغْبَةً وَرَهْبَةً إِلَيْكَ لَا مَلْجَأَ وَلَا مَنْجَا مِنْكَ إِلَّا إِلَيْكَ آمَنْتُ بِكِتَابِكَ الَّذِي أَنْزَلْتَ وَنَبِيِّكَ الَّذِي أَرْسَلْتَ
"I submit my life to you, I turn towards You and leave my work unto you, I lean on you, desire your boons and fear you as there is no other salvation besides you. I believe in the kitab (Book) you have revealed and in the Rasul(Prophet) you have sent.
Prophet Mohammad (S.A.W.) showed (taught a Sahabi) this dua and said: "If after reading it you die in the night, then it is as if you have died on 'Natural Deen' and if you awake in the morning alive then you will have good fortune".
Anas (R.A.) narrates that Prophet Mohammad (S.A.W.) said that if a person retires to bed on the side and recites Surah Fathiha and Surah Ikhlaas (Qul huwa- Allaho Ahad) he is immune from everything besides death.
(Hisnul Hasan from Albazr)
Sahabi (R.A.) requested Prophet Mohammad (S.A.W.) that Prophet Mohammad (S.A.W.) teach him something to recite at the time of retiring to bed. Prophet Mohammad (S.A.W.) said: "Recite Qul Ya Ayuhal Kafiroon, for in it (there is an announcement) to refrain from shirk.
(Mishkat from Tirmidhi)
In some ahadith it is stated that one should sleep after reciting (i.e. not to talk after reciting it).
(Hisnul Hasin from Albazr)
Ayesha (R.A.) narrates that when Prophet Mohammad (S.A.W.) used to go to the room for sleep, he used to recite Suras Ikhlaas, Falaq, Nass and blow onto his hand (palms) in such a manner that the saliva would drop on them and then he would rub them over his body three times starting from the front of the face.
Beside this he would recite
33 times سُبْحَانَ اللَّهِ
33 times الْحَمْدُ لِلَّهِ
34 times اللَّهُ أَكْبَرُ
He also used to recite Ayatul Qursi as Allah has stipulated that the reciter will be protected throughout the night by the angels and the Satan will not come near.
Also recite this dua three times
أَسْتَغْفِرُ اللَّهَ الَّذِي لَا إِلَهَ إِلَّا هُوَ الْحَيَّ الْقَيُّومَ وَأَتُوبِ إِلَيْهِ
Its virtues are that all the reciter's sins will be forgiven even if it be equal to the extent of the foam in the ocean.
Recite Bismillah while closing doors, covering utensils, and putting off the light (candles etc.)
Prophet Mohammad (S.A.W.) said that when a person enters his bed (to sleep), an angel and a Shaitaan surround him. The Shaitaan whispers 'your awakening will end in evil' and the angel says' end in good". One sleeps after engaging in dhikr, the angels will protect him throughout the night. In order to gain the protection of the angels, it is wise to engage in Dhikr and then sleep.