You will need to choose one of these themes, and develop a thesis around it. For example, the danger of haste is an interesting one.  Your thesis should clearly state your point and purpose.

In Romeo and Juliet, Shakespeare develops the theme of the danger of haste by demonstrating the consequences of haste for a variety of characters.

The most obvious case for haste is obviously the constant dueling.  Characters are ready to fight at a moment’s notice.  In the first scene, a stroll turns into a large brawl.  The citizens all get involved.

Clubs, bills, and partisans! Strike! beat them

down! Down with the Capulets! Down with the

Montagues!(70) (Act 1, Scene 1, p. 12)

This haste to fight is just because the person is from a family with whom the family you are associated with feuds.  It is ridiculous, and destructive.  This fight leads to the proclamation the prince makes that anyone caught fighting will be severely punished.  This in turn leads to Romeo’s banishment when he kills Tybalt.

Clearly Romeo and Juliet’s hasty marriage is also trouble, and leads to destructive behavior in both of them.  However, it is not the only example of haste.

Another example of haste would be Juliet’s parents’ insistence that she marry.  If they had waited, she would not have needed to fake her death.

Monday! ha, ha! Well, Wednesday is too soon.(20)

Thursday let it be— a Thursday, tell her

She shall be married to this noble earl.

Will you be ready? Do you like this haste? (Act 3, Scene 4, p. 77)

If her parents had not pushed her, she would not have felt trapped and faked her death.  Romeo would not have killed himself thinking she was dead.  It would have saved both their lives.