Shabbat HaGadol

Why is it called Shabbat HaGadol?

1. Some explain that it's called Shabbat HaGadol because that was the Shabbat when a miracle occurred for the Jews in Egypt that the Egyptians didn't say anything when the Jews took sheep, which was the Egyptian god, in order to slaughter them for Pesach.
2. As Am Yisrael left Mitzrayim on the 15th of Nissan (Thursday), the previous Shabbat would have been the 10th of Nissan, the same day Moshe asks K'lal Yisrael that "they shall take every man a lamb, according to the house of their fathers, a lamb for a house." Tosfot explains that this action interested and angered the Egyptians, and so the firstborn pleaded to Pharaoh to free Am Yisrael, but he refused. And so, as a result, the firstborn attacked their fathers. The greatness is derived from the damage Hashem did to Egyptian society in this sense.
3. See Sfat Emet Shabbat HaGadol for more.
4. It wasn't established on the date of the 10th because it was the date of Miriam's death and we don't want to establish a holiday for that day.

Haftarah

1. There are a number of Minhagim about which Haftara to read when Erev Pesach is on Shabbat HaGadol, and each community should follow its own custom.

Drasha of the Rabbi

1. The minhag is for the Rabbi of the community to give a Drasha on Shabbat HaGadol on Hilchot Pesach. If Shabbat HaGadol falls out on Erev Pesach, the Drasha should take place a week earlier.
2. If the Rabbi who usually gives the Drasha on Shabbat HaGadol is in mourning and there’s no other Rabbi to make a Drasha, it’s permissible to give the Drasha.

Greetings on Shabbat Hagadol

1. The minhag is to greet one another saying "Shabbat Hagadol Mevorach" on Shabat Hagadol.

Reading the Haggadah in advance

1. On Shabbat HaGadol, the minhag is to read the Haggadah from Avadim Hayinu until LeChaper Al Avonotanu.

Sources

Time	Topic
Before Pesach	Month of Nissan - Shabbat HaGadol - Bedikat Chametz - Biur Chametz - Bitul Chametz - Tanit Bechorot - Erev Pesach - Selling Chametz - Erev Pesach That Fell out on Shabbat - Candle Lighting on Yom Tov - Kashering the kitchen for Pesach - Which foods, medications, cosmetics, and toiletries are Chametz? - Kitniyot - Chametz of a non-Jew - Owning Chametz on Pesach
The Seder	Kaddesh - Urchatz - Karpas - Yachatz - Maggid - Rachsa - Motzei Matzah - Maror - Korech - Shulchan Orech - Tzafun - Barech - Hallel of the Seder - Nirtzah - Kriyat Shema Al HaMitah
Pesach	- Setting the Table (The Seder plate) - Arvit of the night of Pesach - Leaning during the Seder - Required Amount of Matzah and Wine for the Seder - The four cups of wine - Matzah
After Pesach	Issru Chag - Chametz which a Jew owned on Pesach - Pesach Sheni