Sweet name, right? These guys are clearly dude-ish. The Night's Watch is the military order that guards the Seven Kingdoms from whatever is up north. Mostly that means that they maintain this giant freaking Wall and send scouting parties to make sure that the wildlings don't get too close. The wildlings are just people, but they are people who are outside of the law (kind of like the Mountain Clans). And there actually might also be some real monsters up beyond the Wall, too.
While the Night's Watch used to be a noble profession, most of the people who belong these days are younger sons of noble houses (that is, people who wouldn't inherit anything since everything would go to the first-born son) and criminals who were given the choice to suffer some punishment or join the boys' club. Since the Night's Watch dresses all in black (which is good for… hiding in the snow?), the phrase "to take the black" means to join the Night's Watch.
Since Jon Snow, who joins the Night's Watch, is one of our major POV characters, we meet a lot of characters up there. Here are a few:
Benjen is Eddard Stark's younger brother, and like a good younger sibling, he joined up with the Night's Watch. He's First Ranger, which means that he's in charge of scouting the dangerous area north of the Wall. This doesn't turn out so well for him as he soon goes missing.
His main jobs in this book are (1) to bring Jon up to the Night's Watch and (2) to disappoint Jon by not giving him any special favors. That is, Jon wants to join the rangers immediately, but Benjen makes him go through all the usual training: Benjen makes sure that Jon Snow is a little isolated up there.
And don't you just love that his name "Benjen" gets shortened to "Ben"? So many of these fantasy characters have names that seem somewhat normal: Ben, Jeyne, Robert, Ned… the list goes on.
Okay, so "Jeor" isn't really a normal name in our world. Jeor is kind of a substitute father for Jon Snow. He's the Lord Commander of the Night's Watch, just like Eddard Stark was the lord of the north. Also, whereas Eddard couldn't (wouldn't) give his special Valyrian steel sword to Jon, Jeor does gives Jon a Valyrian steel sword that was supposed to go to his own son, Jorah.
Like a good father, Jeor is nurturing and forgiving (as he forgives Jon for running away in 71 Jon 9), but he also corrects Jon and shows him the right way. Like Donal Noye below, one of Jeor's main roles in this book is to help Jon Snow grow up and find his place in the world.
Jeor is sixty-eight years old (22 Tyrion 3.39) and he's one of the few characters up in the north who joined the Night's Watch of his own free will. So, in that way, he's a role model for Jon in terms of being true to his duty.
In the grand tradition of fantasy novels, Aemon is a blind man who can really see what's important. So when Tyrion talks, other people laugh, but Aemon sees that Tyrion has greatness in him (22 Tyrion 3). Aemon also sees that Jon is right about Samwell Tarly (42 Jon 5). And most importantly, Aemon saw that his duty to the Night's Watch was more important than his duty to the Targaryen kings, who were family. (He's actually Aemon Targaryen, brother to one of the old Targaryen kings. So he was grand-uncle to the Targaryen king that Robert Baratheon kicked out.)
And if you think about it, Aemon's decision to serve the Night's Watch makes a lot of sense: Aemon could have helped the Targaryens remain kings (maybe), but then the monsters from the north would've come over the Wall and destroyed the whole kingdom. (Or at least, that's the worry.) That's why the Night's Watch is more important than any particular king.
Of course, not everyone in the Night's Watch is here to teach Jon by modeling good behavior. Some characters are, well, jerks. Take Alliser Thorne – please! Thorne is up on the Wall because he fought for on the Targaryen side during the rebellion: Tywin Lannister gave him the choice of death or taking the black. So, that's at least one reason why Thorne is so sour, especially toward Jon Snow. After all, the Stark family did help lead the rebellion against the Targaryens.
(When you think about it, Jon's new family is pretty much full of people who are enemies of his old family. In this book, family can be a mixed blessing, and Alliser Thorne makes sure the Night's Watch is just that for Jon: thanks to Thorne's jerkiness, Jon eventually finds a role for himself as a protector and leader of other recruits.)
Donal Noye ended up on the Wall sort of accidentally: after losing his arm fighting against the Targaryens, Noye decided to take the black. And yet, he's still a nice guy, capable of sympathizing and telling people the hard truths they need to face. If Thorne shows us what a bad teacher can be, Noye shows us how you can learn something from anyone in your life. (In this case, "you" = Jon Snow.) Donal Noye is the one who points out to Jon Snow that he's being a bully to the other new recruits. Thanks to Donal Noye's advice (don't be a jerk, kid), Jon Snow is finally able to make friends up north.
Most of Jon's friends don't get too much screen time, though we often get a quick characterization and maybe something of their history. For instance, Grenn is a big guy who isn't particularly bright (which is why he has the nickname "Aurochs," which is a creature like an ox), whereas Pypar (a.k.a. Pyp) is a little guy who used to travel with some actors. Other close friends of Jon include Todder (a.k.a. Toad) and Halder (a.k.a. Stone Head). These are the friends who stop Jon from running away from the Night's Watch after Eddard is executed. It's amazing to see this group of boys take care of each other when they used to spend their time beating each other up.
But Jon's most important friend is probably Samwell Tarly. Sam gets to tell his whole story about how he ended up with the Night's Watch, even though he's a coward. See, his father, Lord Randyll, wanted a manly man for a son and Sam was a little too sensitive. So his father has a plan: Sam will either join the Night's Watch or he'll be murdered, just to be sure that the son he does like (Dickon) inherits the estate and the family sword.
Well, Samwell clearly has family issues and is something of an outcast from his family, like Jon. In fact, almost everyone in the Night's Watch is kind of an outcast. But of the whole gang, Sam is the boy who needs the most help fitting in. Jon may become friends with Grenn and Pyp, but protecting Samwell gives Jon's life something of a purpose.
We could also add that Sam has a different set of skills to offer than Jon's other friends. That is, Grenn and Pyp are good fighters, just like Jon, but Sam is a good reader and careful observer. In this way, his friendship with Jon is like many other pairings we've seen, like Hodor and Bran, and Bronn and Tyrion.
There are some other recruits up at Castle Black at the same time as Jon: Matthar, Jeren, Albett, Dareon, and Rast. These recruits don't get a lot of attention and only Rast stands out: he's the one boy who plans to follow Thorne's order and beat up Samwell Tarly (until, of course, Jon threatens to let Ghost eat him) (27 Jon 6).
Yoren is older, smelly, filthy, rough, and secretly heroic. He's the recruiter for the Night's Watch, riding south to find convicts and then north to bring them to the Wall. All this travel lets him see what's going on and he sometimes tries to act heroically in response. For instance, he sees Catelyn Stark take Tyrion hostage and then he rides hard for King's Landing in order to warn Eddard about this potentially dangerous action by his wife. And then Yoren finds Arya in the crowd when Eddard is executed and protects her by making sure she doesn't see the execution itself. Yoren is secretly a nice guy: so don't get too attached, because nice guys finish dead in this book, right?
We first meet the Night's Watch in the Prologue, before we know anything else about this fantasy world. The Prologue sets up a few things that we need to know, and it does this primarily through the three rangers that we meet.
First, there's Will, who is our POV for this chapter. He's the classic ex-criminal who took the black. He's here to show how convicts serve in the Night's Watch and also how they're not terrible people. He's served in the Night's Watch for four years (1 Prologue.11). And he gets killed by a wight.
Ser Waymar Royce is the opposite case: he's a young nobleman who took the black because his family had too many sons to care for. He's only been part of the Night's Watch for half-a-year, but he's already in charge. This just goes to show you that a lot of decisions in this world are going to be made according to who is noble and who isn't: Ser Waymar Royce is a good introduction to how power is often based on lordliness and blood rather than experience or smarts. He gets killed by the Others and turned into a snow zombie… uh, we mean "wight."
The third member of the team is Gared, and he's the most experienced of the bunch: he's been in the Night's Watch for forty years. The fact that he's nervous now tells us that something unusual is about to happen, something that hasn't happened in forty years. Also, Gared shows us what happens to deserters, when Eddard Stark executes him as an oathbreaker. Eek.
There are several other members of the Night's Watch that we meet in Jon's chapters. (We kind of wish he was less social and met fewer people, but that's not his style.) These characters may not take huge roles in this book, but they may be important later. You never know. Well, until you read the next books.
Among them are Bowen Marsh, the Lord Steward, who reminds us that the Night's Watch needs planners and cooks and all that sort of support, not just rangers and fighters; Othell Yarwyck, the First Builder, in charge of maintaining the Wall; Jaremy Rykker, who, like Alliser Thorne, ended up on the Wall because he fought for the Targaryen side, but is still a fine guy (which makes it not-so-surprising when he's killed by one of the magically animated corpses); Chett, Aemon's surly assistant; Cellador, the Night's Watch's drunken septon; Clydas, a steward to Maester Aemon; Dywen, a ranger; and Hake and Hobb, cooks.
Hali and Osha aren't actually in the Night's Watch (they don't even let women into the Night's Watch, after all) – they're wildlings. Stiv and Wallen are Night's Watch, but they're deserting their posts (and you know what happens with oath breakers if they get caught). There's no explanation of how these two oath breakers joined up with these wildlings; or how they made it past the Wall and close enough to Winterfell to threaten Bran. But there you have it: there's something so bad out there that these natural enemies (Night's Watch and wildlings) have joined together. In other circumstances, this unity would be a hopeful message.