How is honor shown in Romeo and Juliet?

In this play, honor mostly boils down to family pride.  We never learn exactly why the Montagues and Capulets are feuding, and we only see them fight now over family honor or pride.  The first fight, in Act 1, scene 1, occurs because one man says that his master is better than the other's.  Tybalt gets incredibly angry when Romeo shows up, uninvited, to the Capulets' big party because he feels that the presence of a Montague dishonors his family.  He says to Lord Capulet, "Why, uncle, 'tis a shame" (1.5.92).  His pride is wounded by Romeo's audacity. 

Then, when Tybalt challenges Romeo the next day and Romeo refuses to fight, Mercutio gets involved because he sees Romeo's behavior as a "dishonorable, vile submission" (3.1.74).  Mercutio gets himself killed because he doesn't want Romeo to dishonor the Capulets with his unwillingness to fight, unwillingness that must look like cowardice to Mercutio.