The halacha (Jewish law), relating back to what we were talking about over these last few days and to the question that came up the other day, is this: Can a person say it while in bed? Do they need to be standing up or sitting up? Can they be lying down? What is the exact process?
So the halacha that Amar brings in and everyone follows is this: Yes, as he puts it, it's better to say it standing up, or at least sitting down, sitting straight up. But technically speaking, it's okay if a person is lying down, even while lying down. Again, why? Because you're not fulfilling the mitzvah (commandment) of Shema of the night. You did that in Arvit; you did that again. This is simply a tefillah (prayer) of protection, so it can be said while lying down. However, when we talk about lying down, we do not mean lying on our face or on our back; we mean lying on our side. That's the proper way to lie down, according to halacha, and that's the proper way to say Keriat Shema.
One last detail: in the Shema, our Minhag (custom) is to say Ana (please). Say Ana. If it's before chatzot (halachic midnight), you say Ana. That cannot be said lying down; it has to be said standing up. That's halacha. Have a great day, Kavod (honor).