A Capulet bites his thumb to the Montagues. That offends the Montague so they start a fight. "Nay, as they dare. I Will bite my thumb at them" (1.1.36)
The prince of Verona comes to stop the fight. He then says that the next person to start a fight will be executed. "Once more, on pain of death, all men depart" (1.1.96)
Romeo is sad that Rosaline could not be with him. His friend Benvolio tells Romeo to go to a party of the Capulets so that Romeo could forget about Rosaline after a servant asks them to read some names from the party list. "I pray, can you read anything you see?" (1.2.59)
Romeo goes to the party and falls in love with Juliet. Tybalt sees Romeo at the party and wants to fight him. "O, she doth teach the torches to burn bright!" (1.5.42)
Romeo talks to Juliet and they love each other. So they agree to get married. Friar agrees to Marry them.
Tybalt fights and kills Romeo's friend Mercutio. Then Romeo gets mad and kills Tybalt. Then Romeo gets banished from Verona by the King.