Buffy's Love Life
Angel was Buffy's first love, and her most dangerous, though neither of them knew it. He showed up just after Buffy arrived in Sunnydale, to give her a gift and warn her about the Harvest. Though Buffy told Giles she "really didn't like him", they ended up kissing in Angel. The relationship continued on until Buffy's seventeenth birthday, when they made love, and according to the rules of Angel's curse, he lost his soul. Souless Angelus devoted most of his nights to driving Buffy crazy, (Literally, that's what he was trying to do) but managed to find time to release an earth-devouring demon. Willow recast the curse and gave Angel back his soul, but the demon had already been awakened and Buffy was forced to send her love to hell. For some strange reason Angel returned, after a hundred years (hell time) and Buffy and him got together again. Just before Buffy's graduation, Angel told her he was leaving, to give her a chance at a normal life. Though he left for Los Angeles the day Buffy graduated, they still talk now and then. Their last known meeting was in Forever"
After a few unsuccessful relationships, Buffy met fellow college student, Riley Finn. He was the assistant of one of her teachers. At first they were just friends, but it soon grew beyond that. Then Buffy found out that Riley was part of a secret organization that caught and 'gentled' demons, and he found out that she was the Slayer. They worked together for about a year, then broke up. He rejoined the army in another secret service.
Riley was last seen in As You Were, when he returned to Sunnydale with his wife, Sam, to track down a demon and stop a man called the Doctor, who turns out to be Spike.
Spike first showed up in Season Two, with his insane girlfriend Drusilla. They hung around Sunnydale, while Spike tried unsuccessfully to kill the Slayer. Angelus joined the three for a while, then Spike took Drusilla and left Sunnydale, after betraying Angelus to Buffy.
Spike returned in Lover's Walk after Drusilla dumped him for another demon. Originally he wanted revenge on Buffy, but then tried to force Willow to make a love spell. Finally, he decided the way to get Drusilla back was to torture her until she loved him again, and left.
His next appearance was in Wild At Heart when he did a nice little speech about killing Buffy before he was caught by the Initative. He managed to escape, but not before the Initative implanted a chip in his head which prevented him from harming humans. He stayed with Giles for a while, then moved in with Xander, and began helping the Scooby gang fight demons, then eventually got his own place, an old crypt. He continued to help the Scoobies, and in Crush admits he's in love with Buffy. She's shocked, and makes it clear that she doesn't return his feelings.
When Buffy comes back from the dead, she starts to get closer to Spike, telling him things she couldn't tell the rest of the Scoobies. After Spike discovers that his chip is not affected by Buffy, the relationship gets deeper. They remain lovers until Riley returns and Buffy discovers that Spike was the 'Doctor'. She then tells him that she was only using him, and though he made it clear that he knew and didn't care, she broke up with him. Spike ended up trying to rape her, then left for Africa to try to get the chip removed by a god who lived there. Instead, he was given back his soul. He returned to Sunnydale, and now lives in the basement of the new highschool, haunted by the voices of his past.