The Laws of Krias Shema vol.3, no.21
It is a mitzvah to recite Krias Shema once in the morning and once in the evening. The time to recite Shema in the morning begins when one can recognize an acquaintance from about six feet away, approximately an hour to forty five minutes before sunrise according to many authorities. One can recite Shema until one third of the day passes, which is a time that fluctuates with the length of the day. The optimum time to recite Shema is close to sunrise so that Shemone Esreh can follow immediately with the sunrise. If one did not recite Shema before the third hour he may still recite it until the fourth hour with its blessings.
Shema can be recited while standing or sitting. However, one may not recite it lying down. One who is confined to bed should try to lean on one’s side.
Before one recites Shema he should have in mind that he is performing a positive commandment. One should have the basic intent while reciting Shema that Israel should hear and understand that Hashem is our Lord, He is Hashem who is One over the heavens and the earth.
One must recite Shema with extreme preciseness. One should use a siddur with a carefully prepared text which is accurate and easily readable. One should try to say each word distinctly and not slur the end of one word into the beginning of the next word. For example one should take care to say " v’ahavta es" as opposed to "v’ahavtes". Many siddurim are printed with thin vertical lines to separate words that are easily slurred together. The letter zain should be emphasized so that it does not sound like a samach. One should hear himself when he recites Shema.
One saying Shema should not catch someone’s attention with their eyes or motion with their fingers. However for the sake of a mitzvah one may do so in while reciting the second paragraph.
It is customary to hold the tzitzis while reciting Shema. During the first two paragraphs they are held in the left hand between the pinkie and the ring finger. When one reaches the third paragraph he holds them with his right hand as well.
