What are some character traits of Romeo and Juliet?
The first trait Juliet shows is that she is extremely sheltered. Consider where we first meet her: in her room (conversely, the first time we meet Romeo is on a street).
She is also inexperienced in romantic relationships. While her age is a good indication of that, we can also take the balcony scene as proof of this. Take this exchange:
Thou know'st the mask of night is on my face,
Else would a maiden blush bepaint my cheek
For that which thou hast heard me speak to-night
Fain would I dwell on form, fain, fain deny
What I have spoke: but farewell compliment!
Dost thou love me? I know thou wilt say 'Ay,
'And I will take thy word: yet if thou swear'st
Thou mayst prove false; at lovers' perjuries
Then say, Jove laughs. O gentle Romeo,
If thou dost love, pronounce it faithfully:
Or if thou think'st I am too quickly won,
I'll frown and be perverse an say thee nay,
So thou wilt woo...
She is so uncertain of how to act in this situation, and so she gives Romeo a few options of how she should act. Her insecurity in this shows us a lack of confidence from which he can infer her lack of experience in this sort of situation.
In the beginning of Shakespeare's Romeo and Juliet, Romeo is very lovesick. He's been chasing a girl named Rosaline, with whom he's pretty infatuated, and she has, apparently, been spurning his advances. He is also pretty lusty. When Romeo meets Juliet, however, he does seem very sincere. In fact, before Tybalt kills Mercutio, Romeo was willing to let Tybalt kill him because he doesn't want to harm his wife Juliet's family. Romeo's love for Juliet is in earnest, we can assume, or else he would not be willing to sacrifice his life in this exchange.
Juliet is somewhat more cautious when she and Romeo first meet. She is flattered by his compliments, but she wants to proceed more slowly than he does in the beginning. Although some may characterize her later actions as impulsive and unwise, I would classify Juliet as brave and strong. At not quite fourteen years old, she is willing to drink the potion that will make her appear dead, have her body placed in her family's crypt, and await Romeo so they can run away together. This would be pretty terrifying! Although it doesn't work out, obviously, Juliet's bravery gave her and Romeo their best shot at being together.