Shakespeare was a smart man who understood that comic incidents in a tragic play about young lovers kept the audience entertained and the comedy only intensified the tragedy. Having the comedy and tragedy juxtaposed with each other made each more visible, more understandable. Comic relief is often used to lighten the mood a bit before tragedy strikes again, and Shakespeare uses comic relief with skill. If you are looking for comic scenes, look to the nurse who is a rather bawdy woman who loves Juliet, but is quite unrestrained in her talk such as saying that Juliet might have "suck'd wisdom from teat" which isn't exactly polite conversation. Mercutio is also witty as shown in his Queen Mab speech which teases Romeo about how shallow his "love" for Rosaline truly is. Romeo is just fantasizing about Rosalind, and true love appears with Juliet. Remember that the audience in Shakespeare's time would throw rotten tomatoes etc at the actors if the show was not entertaining.