Robin - Robin is very cool, and he often takes things a bit seriously. Robin was once Batman's apprentice, so he got some of his sweet karate moves from him. He's generally seen as the leader of the Teen Titans, despite having no powers. He is a bit dark and mysterious, but he is friendly and have a sense of responsibility. He is serious, determined, and smart. Not a genius, but definitely smart.
Cyborg - Cyborg is the only one of the Titans that... isn't actually a Teen, but he still acts like a kid. Of course, he is half-robot. Cyborg acts very immature most of the time, but when under a small bit of pressure he turns very serious and on top of things. He is handy and intelligent.
Beast Boy - Beast Boy has the best powers of the group, but because of his lack in leadership, he can't be the head of them. He has the most similarities to Cyborg, who is his best friend, but Beast Boy is hardly ever serious. Beast Boy is classified as annoying and not funny. He has a corny sense of humor other people just don't like. Some people can appreciate him though, and he just has to find those people.
Raven - Raven is the darkest and most mysterious of all of the characters, but she has to be. She has a dark destiny that she thought she couldn't control, and her powers rely on a calm mental state. She's generally sarcastic and condesending, but sometimes she lets her soft side come out. Noise annoys her, and she prefers to be alone. She's often ignored because she's 'different', but that makes her awesome.
Terra - Terra may not be a Titan, but to put it lightly, she's more of a semi-Titan. While friendly and kind, Terra is very insecure. She will listen to what people tell her, and that lead to her downfall.
Starfire - Starfire comes from a different planet, and she's the one that the Titan people know most about. She may not have the best storyline, but we do know her origin and it's not very uncommon. She is generally well-liked, and considered pretty. She is sometimes too friendly and annoying, and that can get under other people's skin. She tends to be too needy and she feels best in the company of other people, even ones that don't like her.