Have you ever been watching Game of Thrones and heard a character spout some weird one-liner and everyone seems to understand but you're clueless? Or has a character made a weird gesture, or, say, burned another character at the stake for reasons that simply aren't clear to you?
Chances are they're practicing one of the many fictional religions of the world of George R.R. Martin's A Song of Ice and Fire. While Westeros and King's Landing are dominated by The Faith, Essos is crawling with too any localized micro-religions to even list. The fractured relationship between Northern and Southern Westeros comes in part because the Northerners worship a whole different set of Gods. Religiously speaking, Ned Stark and the people of Winterfell have more in common with wildlings than they have with the Targaryan, Baratheon, or (who are we kidding) Lannister lineages.So, to understand the world, you need to understand its religions. There are eight religions practiced by major characters, so let's focus on those, but there are many smaller ones throughout the known world. There are divisions within each religion (just ask Cersei after she's imprisoned by her own choice of High Septon), but to keep things clear, we'll just focus on the overriding doctrines. That should make it easy for you to decide which religion in Game of Thrones is most worth following!
The Old Gods of the Forest
Motto: "By the Old Gods and the New"
Pantheon: Innumerable nature gods
Geographic Area: Northern Westeros and Beyond the Wall
Notable Followers: Ned Stark, Santa Stark, Roose Bolton, Jorah Mormont
The Many-Faced God of Death
Clergy: Faceless Men
Pantheon: The faceless men consider all other gods to be disguises worn by their Many-Faced God
Geographic Area: Bravos
Notable Followers: Jaqen H'ghar
Weirdest Ritual: People who have had enough simply walk into the House of Black and White, poison themselves, and die on the floor.
Clergy: Red Priests and Red Priestesses
Pantheon: R'Hllor, a.k.a. The Lord of Light
Geographic Area: Essos
Notable Followers: Melisandre, Beric Dondarrion, Thoros of Myr
Weirdest Ritual: Melisandre can predict the future using the blood of kings. She also likes sacrificing people to the flames for what is essentially "good luck" in war.
Motto: "May the [insert God name here] [insert whatever that God does here] you." (Example: "May the Father protect you.")
Clergy: Septons and Septas led by The High Septon
Pantheon: The Seven (The Father, The Mother, The Maiden, The Crone, The Warrior, The Smith, and The Stranger)
Geographic Area: Southern Westeros
Notable Followers: The High Sparrow, Cersei Lannister, Margaery Tyrell