Inuyasha (accent on Inu, yasha pronounced as one syllable.)
Inu's name, roughly translated, means dog demon. This is because his father, Inu no Taisho (literally translated, Dog father, no pun intended, I'm sure) was a giant white dog youkai. His mother, however, was a human. This makes Inuyasha a hanyou, or half-youkai.
You can easily tell him on the show because he has long white hair, dog ears, and always wears a lot of red. Or, if it happens to be the night of no moon, Inuyasha's hair turns black, his ears are replaced with human ones, and a lot of his strength goes away. Also, every once in a while, he will become excessively pissed off, causing him to revert to full demon form. You can tell him in this form because his eyes turn red and purple stripes appear on his cheeks. (You may not want to stay around long to look at this form.)
Inuyasha is a very complex individual. Being hanyou, he is distrusted by humans and youkai see him as worthless, his blood tainted. Growing up, it seems that his mother was the only person who thought anything of him, and seeing as he aged much slower than her (roughly ten human years to one hanyou year) she must have died when he was still very young, maybe from eight to ten. After that he set out trying to get at the shikon no tama. During that particular quest, he met up with possibly the only person who did not hate him on sight: Kikyo. He slowly fell in love with Kikyo, eventually to the point where he gave up the goal of becoming full youkai to instead full human., so he could be with her. This was a dream future for him, but was shattered when Kikyo, instead of giving him the jewel as planned, instead accused him of stealing it and shot an arrow pinning him to a tree for fifty years. This pretty much destroyed any chance of him trusting anyone again.
He is also afraid to feel for humans, because his feelings for his human mother are tinged with shame. He is of the opinion that all youkai are evil, and is proven time and again to be right. He trusts no one but himself, and with his feelings warring between love for Kikyo, his morals, his desire to become full demon, and his love for Kagome growing against his will, not even that is certain to stay for long.
Weaknesses: Not as strong as regular youkai, and sometimes has difficulty controlling his sword. He feels a lot for Kagome, so kidnapping/possessing her would be a good bargaining chip for getting jewel shards, however, killing her will end badly for you. She 'died' about three times in the beginning of the show and each time it only served to make him pissed enough to kick some serious ass. He seems to have difficulty protecting his midsection, and it's remarkably easy to get in a hit there.
Attacks: Iron reaver soul stealer. (sankon tessau) It's the most basic of attacks, and seems to come from his claws. In the anime it is portrayed as three parallel curved of yellow light.
Blades of blood. (hijin kessou) This is a secondary attack, and is normally not used until later in battle, mostly because it won't work unless his fingers are covered in blood. This blood is normally his own, but I do think he’s used Kagome's at least once.
Tetsusaiga:(or tessaiga) This is not technically an attack. Tetsusaiga is his sword, which was taken from his father's tomb. It is made from one of his father's fangs, and is therefore nicknamed 'the fang.' Creative, no? The literal translation is “iron-crushing fang”
The fang has two attacks, the windscar, (kaze no kizu) which is portrays as yellow rays of light. They can take out a hundred demons in one swing. Then there is the backlash wave, (bakuryuuha) which takes a demon's energy and sends it back at them. The tetsusaiga can also break through barriers.
The key to tetsusaiga is that it needs to be wielded by a human, or half-human. Demons cannot touch it. Then, after they actually get a hold of it, it needs to be transformed. Tetsusaiga in it's untransformed state is basically a beat up piece of crap. This is a defense mechanism, to keep it from being stolen, I guess. In it's transformed state, however, it grows to the shape of a fang, almost five feet long. Tetsusaiga cannot be transformed by Inuyasha when he is in his full human or full demon form. (which sucks cuz that’s when they invariably run into trouble.)
He is very very strong, able to pick up really big rocks and such, and to wield the giant tetsusaiga. He also heals very fast, and is hard to kill. Three sword thrusts took about a day to heal, leaving no scar at all. When Sesshoumaru punched straight through his stomach he passed out, but that only lasted a few minutes. It took a few days to heal, but only because he wouldn't sit still, and eventually had to be forcibly detained.

Miroku (Mee- ROH- koo)
Miroku is a monk, (houshi) though it's hard to believe. He's a total perv. The first time he met the group, it was just Shippo, Inuyasha, and Kagome. He stole their jewel shard and tried to kill Inuyasha, then asked Kagome to bear his child. Neither of these things went over well with Inuyasha. However, after demonstrating his usefulness in battle, he was reluctantly allowed to join the group... Provided he didn't hit on Kagome anymore. I'm sure there's a word for what he wears, but I don't know what it is. It's blue and black. He also carries a long staff. His hair is short and a little bit of it is tied back. His eyes are really dark blue, but you can only tell when it's bright out.
Miroku is destined to die the way his father and grandfather before him have: To be sucked into their wind tunnel, a curse from Naraku. We don’t know exactly why the family was cursed this way, but each generation is in turn cursed. Miroku seeks to destroy Naraku before he is killed, because it is the only way to break the curse.
Despite being doomed, he tries to keep up a good attitude. He can't figure out women (yeah, what guy can) and has given up on romance and gone straight to groping. Every women he meets he asks to bear his child. I guess he needs a kid to destroy Naraku in case he fails. He gets a lot of slaps for that, but every once in a while he gets a 'yes' in which case it's usually a really old or ugly woman, and he gets out of it.
As of recently, he's fallen for Sango, but that doesn't stop him from asking... Or touching... Every woman he meets. It's hard for her to tell whether or not he likes her because he is incredibly zen about pretty much everything. He wants her to be happy, and if she's happy with him, good, fine, if she's happy with someone else, that's just fine too.
Miroku is a doubtful monk, as well, because he always seems to sense and evil presence above the wealthiest house in the village. His companions noticed this almost immediately. He is not above tiny fibs, such as telling people he can help them with his spiritual powers... But only in the morning, and would they mind letting him stay for the night?
Despite this, he is loyal to his friends, and always willing to lend a hand.
Attacks: He has his kazaana, or wind tunnel. It is located in his right hand, and unless it is covered with prayer beads, it will suck up pretty much anything in it's path. He also has a staff with a gold head, which is useful for blocking shots with swords, and beating stuff over the head with.
He can also use spell scrolls, pieces of paper which, when stuck to various items, exorcise youkai, and keep them at bay. (this even works on Inuyasha.) They can do various things to youkai and hanyou, such as rendering buildings and such invisible, and paralyzing them. He has various nick-knacks, such as a bracelet made of prayer beads which rendered the wearer invisible to a youkai, and of course, the prayer beads which keep the kazaana at bay.
He also has the ability to erect temporary barriers, which keep things such as poison webbing at bay.
Weaknesses: He's a sucker for a pretty girl. Or a moderately good-looking girl. Actually, just girl. He is also vulnerable to Naraku's poisonous insects, which render the kazaana useless, because if he sucks them in he is poisoned. He is also moderately weak, as far as characters go, just because he's human.

Kagome (Kah GO may)
Kagome is the required schoolgirl. She is the only character who is not from the feudal era, instead, she fell into a magic well transporting her back to feudal times. She is the reincarnation of Kikyo, which is why she had the jewel inside her body. Her soul is a hot commodity, and is always getting stolen. She an sense jewel shards, which is pretty much the only thing she's good for, seeing as a day can hardly go by where she doesn't get herself in some kind of trouble, and need to be rescued.
You can tell her because she has black hair and excessively big eyes. She always wears her school uniform, even in the feudal era. It's a short green skirt, a white sweater, black shoes and white knee socks.
There's not much to say on the subject of Kagome, seeing as she is a fairly well-balanced individual. She grew up in modern times, and is not as well acquainted with the monsters and demons as the others, which makes her kind of a burden, being unable to catch the simplest of traps. She does like Inuyasha a bit, but I think this is more from "I can help him" syndrome than actual love. (I always downplay the love, I don't know why.)
She is jealous of Kikyo, because Inuyasha loves her, and loved her long before he met Kagome, and continues to love her even though she is dead and seems to hate him. She is also jealous of Kikyo because the miko had greater powers than she will ever have, and she feels the need to be as good as Kikyo.
Attacks: Her most prominent attack is the ability to shoot sacred arrows, which disrupt spells, and render Kanna's mirror useless. These can also disrupt Kagura's wind spells for long enough for a wind scar to build up.
Her other two attacks are focused mainly on Inuyasha, the most famous of which being the 'osuwari,' meaning 'sit.' Whenever she says this in Inuyasha’s presence, the beads around his neck drag him to the ground with considerable force. This is the result of a spell set by Kaede, to give Kagome some protection against him, or he would have easily killed her to get the jewel. Although this is no longer an issue, the beads do come in handy when he's being a jerk, particularly if he's being a jerk from the top of a tree.
The less famous is not actually an attack. It's the famous sentence "I'm going home." This is also used mainly against Inuyasha, because he hates it when she goes home. She always follows through on the threat, and remains in her own time usually until Inuyasha comes to get her, or until she can't bear it any more.
Weaknesses: She's pretty weak, and usually needs Inuyasha to rescue her. She is very easy to possess, if only for a short period.

Sango (Sahn- go)
Sango is always either in casual clothes, a green skirt, and a pink shirt, or in her armor, which is black and pink. She has black hair pulled back into a ponytail, and red eyeliner. She always carries around a huge boomerang, made from the bones of youkai.
She comes from a village of youkai slayers, which were destroyed by Naraku, and so she seeks revenge.
Sango has nothing left. Her family was killed when Naraku possessed her brother, Kohaku, and forced him to kill her father and the other professional demon slayers. She was the only survivor. When she returned to her village, she found everyone dead, killed by Naraku in search for jewel shards. Naraku then told her it was Inuyasha who killed them. When that was sorted out, she joined the group in search of Naraku. Her plight was not helped any when she came across Kohaku, still under Naraku's spell. He had no memories of her, and tried to kill her. This isn't really relevant, but that's what she's up against: a killer sibling. (Yeah, yeah, aren't you special.)
Attacks: The boomerang, again. It's huge, powerful, and can take apart a lot of demons at once. It's easily avoided, though, and not too indestructible. She's also good in hand-to-hand combat, as well as a good deal of talent with a sword. Kirara may not count as an attack, but the giant firecat follows Sango's orders, and she can cause some damage.
Weaknesses: If you can avoid the boomerang and the cat, you're set.

Kirara
Kirara is a firecat. Or, to be more precise, a demon. She can be small and cute or huge and scary, depending on how she feels. She was given as a kitten to Sango,and they have a close bond. Kirara would do anything for Sango.
In her larger form, she can fly and can carry up to three people.
You can tell her because she’s a yellow and black cat with two tails.

Shippo
Shippo is a kitsune (fox demon) kit. His father was killed by the Thunder Brothers, and his mother is also dead. He can transform into pretty much whoever he wants, however, he still has a bushy orange tail.
After his parents were killed, Shippo took to looking up to Kagome. She protects him from Inuyasha, who’s always getting mad at the kid. He’s usually the one who persuades Inuyasha to go down the bone eater’s well after Kagome. And, like most young kids, he has no idea when to keep his mouth shut.
Attacks: He has an assortment of children’s toys, such as a top which he can make bigger, and a little statue, which also grows. He has foxfire which is weak, but sometimes still effective.
Weaknesses: He’s a little kid. You can pick him up by his shirt collar and he’s totally defenseless.

Myouga
Myouga is a flea who was a friend of Inuyasha’s father. He is generally knowledgeable of people, places, and things. He’s useful when Inuyasha’s having a problem with his sword, or when there’s some spell nobody can figure out. However, in battle, he’s nowhere to be found. He always goes wherever it’s safest for him to be.
Also, he can suck out poison, but takes a lot of blood along with it.
Attacks/weaknesses: we’d probably figure out if he stuck around long enough to see any.