Sleeping according to the Sunnah of Allah's Messenger

(a) Sleep early : Sleeping early is a healthy habit and it was the practice of Allah's Messenger (sallallahu alaihi wa-sallam) to sleep directly after performing the Isha prayer. Abu Barzah al-Aslami (radhi allahu anhu) said that the Prophet (sallallahu alaihi wa-sallam) used to prefer to delay Isha, and he did not like to sleep before it or talk after it.”  [Saheeh al-Bukharee]

(b) Sleep in a state of taharah (purity) : Ibn Abbas (radhi allahu anhu) reported that Allah's Messenger (sallallahu alaihi wa-sallam) said: “Purify these bodies and Allah will purify you, for there is no slave who goes to sleep in a state of purity but an Angel spends the night with him, and every time he turns over, [the Angel] says, 'O Allah! Forgive Your slave, for he went to bed in a state of purity.'”
[Reported by at-Tabaranee. See Saheeh al-Jamee (3831)]

(c) Choose a suitable bed : Excessive luxurious or soft bed provokes laziness and makes one sleep more and become negligent. Aa'ishah (radhi allahu anha) narrates that the pillow of the Prophet (sallallahu alaihi wa-sallam) on which he slept at night was made of leather stuffed with palm fibers.”
[Abu Dawood and Musnad Ahmad. Saheeh al-Jamee (4714)]

Once Umar Ibn al-Khattab (radhi allahu anhu) entered upon the Messenger of Allah (sallallahu alaihi wa-sallam) when he was lying on a mat of palm fibers that had left marks on his side. Umar (radhi allahu anhu) said: “O Messenger of Allah, why do you not get something more comfortable than this?” He (sallallahu alaihi wa-sallam) said: “What do I have to do with this world? My relationship with this world is like that of a traveler on a hot summer's day, who seeks shade under a tree for an hour, then moves on.”
[Musnad Ahmad and al-Hakim. Saheeh al-Jamee (5545)]

(d) Cleaning the bed and lying on the right side :
Abu Hurayrah (radhi allahu anhu) reported: “The Prophet (sallallahu alaihi wa-sallam) said: “When any one of you goes to bed, let him clear his bed by hitting it with his garment, for he does not know what may have come onto it. Then let him lie down on his right side…”
[Saheeh al-Bukharee and Saheeh Muslim]

(e) Reciting the Adhkaar (supplications) mentioned in the Sunnah before sleeping : There are a number of Adhkaar prescribed in the Sunnah before going to bed, amongst them are reciting the last verses of Soorah al-Baqarah, reciting Soorah al-Falaq and Soorah al-Nas and Soorah Ikhlas blow in the palms and wipe as much of the body possible, starting from the head, face and then the front of the body doing it three times. [Saheeh al-Bukharee and Saheeh Muslim]

Ali Ibn Abi Talib (radhi allahu anhu) reported that when the Prophet's daughter, Fatima (radhi allahu anha) came to him and asked him for a servant, he (sallallahu alaihi wa-sallam) said to her and Ali: “Shall I not teach you something that will be better for you than a servant? When you go to bed, say 'SubhanAllah' thirty-three times, 'Al-hamdulillah' thirty-three times, and 'Allahu Akbar' thirty-four times. This is better for you than a servant.” [Saheeh al-Bukharee and Saheeh Muslim]