In Shakespeare's Romeo and Juliet, what are some different character traits possessed by the young lovers?
Romeo is quite emotional and rather impulsive. For just about the entirety of the first act, Romeo is moping around and pining away as a result of his unrequited love for Rosaline. His father says that he weeps every morning, "augmenting the fresh morning's dew," and shuts daylight out. Even when his friends try to cheer him up and get him to crash the Capulets' party with them, he moans about how he doesn't feel like it. Further, the day he marries Juliet in secret, Tybalt challenges him, and though Romeo initially refuses to fight, when Tybalt kills Mercutio, Romeo impulsively murders Tybalt in the street where everyone can see. Had he been even a little thoughtful, he would not have done this (knowing the punishment is death). Then, later, when he learns he's been banished, rather than be grateful, he cries some more and considers death a better alternative. He seems, in many ways, immature as a result of his emotional volatility.
Juliet, on the other hand, is often the more practical of the two, and she is very dedicated and loyal. She is the one who suggests marriage, and tells Romeo how to proceed to get news to her (via the nurse she sends to him). She braves her father's awful temper and terrible threats when he orders her to marry the County Paris, and she opts for a frightening plan to fake her own death in order to be with Romeo instead. Even after Romeo rashly slays Tybalt, she remains loyal to him. Her loyalty to Romeo -- despite his defects -- really drives the plot forward though it, sadly, also leads to the play's tragic end.