Because the literature surrounding the Shema is quite vast, I will bring only general essentials below.
Text of the Shema, referenced below:
Deut. 6
שְׁמַע יִשרָאֵל יי אֱלהֵינוּ יי אֶחָד:
בָּרוּךְ שֵׁם כְּבוד מַלְכוּתו לְעולָם וָעֶד:
Deut. 6
וְאָהַבְתָּ אֵת יי אֱלהֶיךָ בְּכָל לְבָבְךָ וּבְכָל נַפְשְׁךָ וּבְכָל מְאדֶךָ: וְהָיוּ הַדְּבָרִים הָאֵלֶּה אֲשֶׁר אָנכִי מְצַוְּךָ הַיּום עַל לְבָבֶךָ: וְשִׁנַּנְתָּם לְבָנֶיךָ וְדִבַּרְתָּ בָּם בְּשִׁבְתְּךָ בְּבֵיתֶךָ וּבְלֶכְתְּךָ בַדֶּרֶךְ וּבְשָׁכְבְּךָ וּבְקוּמֶךָ: וּקְשַׁרְתָּם לְאות עַל יָדֶךָ וְהָיוּ לְטטָפת בֵּין עֵינֶיךָ: וּכְתַבְתָּם עַל מְזֻזות בֵּיתֶךָ וּבִשְׁעָרֶיךָ:
Deut. 11
וְהָיָה אִם שָׁמעַ תִּשְׁמְעוּ אֶל מִצְותַי אֲשֶׁר אָנכִי מְצַוֶּה אֶתְכֶם הַיּום לְאַהֲבָה אֶת יי אֱלהֵיכֶם וּלְעָבְדו בְּכָל לְבַבְכֶם וּבְכָל נַפְשְׁכֶם: וְנָתַתִּי מְטַר אַרְצְכֶם בְּעִתּו יורֶה וּמַלְקושׁ וְאָסַפְתָּ דְגָנֶךָ וְתִירשְׁךָ וְיִצְהָרֶךָ: וְנָתַתִּי עֵשב בְּשדְךָ לִבְהֶמְתֶּךָ וְאָכַלְתָּ וְשבָעְתָּ: הִשָּׁמְרוּ לָכֶם פֶּן יִפְתֶּה לְבַבְכֶם וְסַרְתֶּם וַעֲבַדְתֶּם אֱלהִים אֲחֵרִים וְהִשְׁתַּחֲוִיתֶם לָהֶם: וְחָרָה אַף יי בָּכֶם וְעָצַר אֶת הַשָּׁמַיִם וְלא יִהְיֶה מָטָר וְהָאֲדָמָה לא תִתֵּן אֶת יְבוּלָהּ וַאֲבַדְתֶּם מְהֵרָה מֵעַל הָאָרֶץ הַטּבָה אֲשֶׁר יי נתֵן לָכֶם: וְשמְתֶּם אֶת דְּבָרַי אֵלֶּה עַל לְבַבְכֶם וְעַל נַפְשְׁכֶם וּקְשַׁרְתֶּם אתָם לְאות עַל יֶדְכֶם וְהָיוּ לְטוטָפת בֵּין עֵינֵיכֶם: וְלִמַּדְתֶּם אתָם אֶת בְּנֵיכֶם לְדַבֵּר בָּם בְּשִׁבְתְּךָ בְּבֵיתֶךָ בְלֶכְתְּךָ בַדֶּרֶךְ וּבְשָׁכְבְּךָ וּבְקוּמֶךָ: וּכְתַבְתָּם עַל מְזוּזות בֵּיתֶךָ וּבִשְׁעָרֶיךָ: לְמַעַן יִרְבּוּ יְמֵיכֶם וִימֵי בְנֵיכֶם עַל הָאֲדָמָה אֲשֶׁר נִשְׁבַּע יי לַאֲבֹתֵיכֶם לָתֵת לָהֶם כִּימֵי הַשָּׁמַיִם עַל הָאָרֶץ:
Num. 15
וַיּאמֶר יי אֶל משֶׁה לֵּאמֹר: דַּבֵּר אֶל בְּנֵי יִשרָאֵל וְאָמַרְתָּ אֲלֵהֶם וְעָשוּ לָהֶם צִיצִת עַל כַּנְפֵי בִגְדֵיהֶם לְדרתָם וְנָתְנוּ עַל צִיצִת הַכָּנָף פְּתִיל תְּכֵלֶת: וְהָיָה לָכֶם לְצִיצִת וּרְאִיתֶם אתו וּזְכַרְתֶּם אֶת כָּל מִצְוֹת יי וַעֲשיתֶם אֹתָם וְלא תָתוּרוּ אַחֲרֵי לְבַבְכֶם וְאַחֲרֵי עֵינֵיכֶם אֲשֶׁר אַתֶּם זנִים אַחֲרֵיהֶם: לְמַעַן תִּזְכְּרוּ וַעֲשיתֶם אֶת כָּל מִצְותָי וִהְיִיתֶם קְדֹשִׁים לֵאלֹהֵיכֶם: אֲנִי יי אֱלהֵיכֶם אֲשֶׁר הוצֵאתִי אֶתְכֶם מֵאֶרֶץ מִצְרַיִם לִהְיות לָכֶם לֵאלהִים אֲנִי יי אֱלהֵיכֶם. אֱמֶת:
Rambam, Hil. Kriat Shema 1:1
The Shema is read twice every day,—in the evening and in the morning, as it is said, "and when thou liest down and when thou risest up" (Deuteronomy 6:7), the phrases in this text meaning at the time when men are lying down, that is, at night, and at the time when they have risen, that is, by day.
1:2
What does one read? Three sections as follows: the section beginning, "Hear, O Israel" (Deuteronomy 6:4-9); that commencing, "And it shall come to pass" (Deuteronomy 11:13-21); and that commencing, "And the Lord spoke" (Numbers 15:37-41). The section beginning, "Hear, O Israel" is recited first, because it sets forth the duties of acknowledging the Unity of God, loving Him, and studying His words. This is the great and essential matter on which all depends. Then, the passage beginning, "And it shall come to pass" is read, this containing a charge to fulfill all the other commandments. Finally the section concerning Fringes is read, as it also contains a charge to remember all the commandments.
1:4
When reciting the Shema, after concluding the first verse, one repeats in a low tone the sentence, "Blessed be the name of His glorious sovereignty for ever and ever" and then resumes the reading of the first section in the regular order from the verse, "And thou shalt love the Lord, thy God,…"to the end of the section.
1:9
When is the time for reading the Shema? In the evening, the duty is correctly performed if it is read at any time from the first appearance of the stars till midnight. If one however transgressed and delayed, but read the Shema before daybreak, he has discharged the obligation. The Sages fixed midnight as the limit only in order to prevent complete violation.
1:11
When is the right time for reading the Shema by day? To observe the precept properly, one should begin reading it before sunrise, so as to conclude the recital of the Blessing after the Shema exactly at sunrise. This interval is about a tenth of an hour before the Sun rises. One who deferred reading the Shema till the Sun had risen, has discharged his obligation—the period for reading the Shema being extended, for one who delayed, to the end of the first three hours of the day.
1:13
If one reads the Shema after the first three hours of the day are gone, even though he had been unavoidably prevented from doing so earlier, he has not fulfilled the duty of reading the Shema at the right time. He is in the same category with one who reads the Torah. Still he recites the blessings that precede and follow it, at any part of the day, even if he delayed the reading till after the first three hours of the morning had elapsed.