It is best to recite all 3 paragraphs of Shema next to your bed. The words, together with Kayl Melech Ne’eman add up to 248 to protect your 248 limbs. At least recite the first paragraph. (ShA1 – MB1)
Do not eat, drink or speak after Krias Shema – just go right to sleep. If you are silent and still, it isn’t considered a hefsek even though a lot of time passes before you fall asleep. (Rama1 – MB3)
If you urgently need to drink or speak, it is allowed – just repeat the Shema again afterwards. However, if you already said Hamapil, drinking and talking will be an interruption between the beracha and the sleep. (MB4)
Make sure your hands are clean before the recitation. (MB5)
What body position should you be in? If you need to fulfil the nighttime Krias Shema, it isn’t correct to recite it laying down. But, if you already fulfilled Krias Shema and you are now just saying it for Krias Shema She’al Hamitta, you don’t have to be machmir to be sitting or standing. But, the problem of laying on your side is that you might fall asleep before you finish. (MB6 – ShaH10)
You can say Hamapil as long as you are going to sleep at night (until dawn). Hamapil was not instituted for a day sleep. (BeH “somooch”)
There are 3 things to say: Krias Shema, Hamapil and the p'sukim listed in Shulchan Aruch and printed in the siddurim. In which order? If your nature is to fall asleep during the recital, it’s best to say Hamapil all the earlier – the Shema and p'sukim are just for protection and are not considered a hefsek. If you aren’t prone to falling asleep before you finish, it is best to say Shema, the p'sukim, and then Hamapil at the end. (ShA1 – MB2 – ShaH8)
If you can’t fall asleep, keep reading the first paragraph of Shema again and again until sleep overtakes you. Another option is to say p'sukim of rachamim or think words of Torah. (Rama1 – MB7)
If you think you might not be able to fall asleep, do not say Hamapil. (BeH “somooch”)
If one is sick, it is enough just to recite the first paragraph of Shema and Hamapil alone. (MB9)
Before retiring, a person should search the deeds of his day. If he finds any transgression, confess and resolve not to do it again. Especially on flattery, lies, levity, lashon horah and bittul Torah. One should forgive anyone who offended or hurt him. (MB9)
A man should not sleep in a room by himself behind a locked door, rather keep it open to where other men are found. People are accustomed to be lenient with this. (MB9 – ShaH17)
Be in the habit of sleeping on your side. Prakdon is forbidden – that is flat on your back or on your belly with your face stuck downwards. (MB6)
Be tsanua when taking off your clothes for bed. (ShA2)
The following people need protection from mazikin: – Sick. – Women after birth. – Chassan. – Kalla. – Mourner. – A talmid chochom (when he is alone in the dark night). (MB9)