Bios
Faith: Perhaps the biggest thing about Faith that appeals to people is that so little is known about her. Yet you have a clear picture of who she is. It is generally agreed that she at the least grew up in Boston, and was likely born there. It is also widely agreed that she is younger than Buffy and the others, (I don't remember it being mentioned before though.) She may have had a bad childhood, abusive parents etc. In fics it's often said that Faith was sexually assaulted.
It is known that her mother is dead, but nothing else was mentioned about her family. After accidently killing a person, Faith seemed to slide into insanity, eventually helping the Mayor before she was put into a coma by Buffy. It is important to note that when Faith murdered the deputy Mayor, Xander tried to help her. Faith tried to kill him for his troubles, but many F/X shippers will tell you that she had some secret reasons for doing it...
Xander: Okay, although Xander is the first Slayerette, and the male lead of Buffy, little is known for sure about him. We know that his first girlfriend was Willow and the relationship went sour after Xander stole her Barbie, they were five. We know that until Buffy came to town, Xander hung out with Willow, Jesse and Amy.
Despite claiming that he hides from Danger, Xander is the first one into the fray, always leading the charge. So despite what he thinks about himself, Xander is the biggest hero on the Scooby Gang, as he has nothing but his wits about him and yet he's litterally saved the world by himself.
You could say that Xander's initial reaction to Faith, was lust at first site, and worship after first story. Of course, after hearing how she saved a group of Baptists in the raw, I fell in love myself, I'm getting off track aren't I this isn't an F/Jason site is it? Oh but how I wish it was...
Faith/Xander
*Warning: Twisting and Creation
of Sub Text Ahead...*
Okay first, we have to talk about "The Zeppo" don't we? Not much need for Sub-text here is it. Xander saves Faith, Faith gets worked up, and bada-bing bada boom, Xander is no longer a virgin. Of course she kicked him out afterwards, but hey we'll get back to that.
In the episode Consequences, Xander is dead set on helping Faith. Despite what Buffy says about Faith not caring about the men she's slept with. You can see, that Xander has some big time feelings for Faith. Sure, you could say he's just out to help a friend. Those who are thinking that, answer me this, has Xander ever been that adament about helping Oz, or Giles, or even Willow? No. The only one he's tried to help that much is Buffy.
Now the big thing that puts a crimp in Faith/Xander as a couple is a little problem with her strangling him. She accused him of just helping her so he could get her back into bed.
Many Faith/Xander shippers deal with Consequences by saying that Faith was frightened by Xander, who may have been the first person who ever actually cared for her and tried to get him to step back. Some argue that like Buffy, Faith was afraid that Xander would be hurt the closer she got to him. Others still simply re-write history so that Faith didn't kill the deputy mayor.
More Subtext to come...