I was originally going to answer that the reader learns more about Tybalt from his own actions, because I was thinking about Act 1, Scene 5. That's the scene where Tybalt wants to have Romeo thrown out of the party. After looking at the text though, I believe that an audience learns more about Tybalt through the words and actions of other characters. In Act 1, Scene 5, Capulet and Tybalt argue over what to do with Romeo, but when you actually look at the text, Tybalt says next to nothing. Capulet does all of the talking.
CAPULETHe shall be endured.What, goodman boy! I say, he shall. Go to.Am I the master here, or you? Go to.You’ll not endure him! God shall mend my soul,You’ll make a mutiny among my guests.You will set cock-a-hoop. You’ll be the man!TYBALTWhy, uncle, ’tis a shame.CAPULETGo to, go to.You are a saucy boy. Is ’t so, indeed?This trick may chance to scathe you, I know what.You must contrary me. Marry, ’tis time.—Well said, my hearts!—You are a princox, go.Be quiet, or—More light, more light!—For shame!I’ll make you quiet.—What, cheerly, my hearts!
I will withdraw, but this intrusion shallNow seeming sweet, convert to bitterest gall.
More than Prince of Cats. Oh, he’s the courageous captain of compliments. He fights as you sing prick-song, keeps time, distance, and proportion. He rests his minim rests—one, two, and the third in your bosom. The very butcher of a silk button, a duelist, a duelist, a gentleman of the very first house of the first and second cause. Ah, the immortalpassado, the punto reverso, the hai!