Much Ado's main focal point and plot device is the readiness of the characters to accept error and misinformation. This is a common method of comedy in Shakespeare's plays. Don John's false presentation of Hero is the most important incident in a series of erroneous reports and misunderstandings. While Don John, the evil brother, and his cohort maliciously mislead their intended victims, Don Pedro benevolently tricks Benedick and Beatrice. Dogberry is fully capable of confusing himself and everyone else.
Disguise, another source of error, is also a prominent motif in the play. At the masque in 2.1, Beatrice and Benedick converse in masks, and their dialogue, more bitter and biting than usual, marks the extreme extent of their hostility. In the same scene Claudio is pretending to be Benedick when Don John tells him that Don Pedro loves Hero. More important, the play turns on Margaret's use of a disguise, Hero's clothes, as part of Don John's plot to slander Hero. The episode is lent futher mystery and confusion by being only reported (in 3.3 by Borachio and in 4.1 by Claudio) and not actually seen on stage.
It has been suggested that Shakespeare's title "Much Ado About Nothing" may relate to the term "Noting" or "to take notice". If this is the case, then there is much ado about "noting". Both Beatrice and Benedick overhear or "note" conversations that have been designed to make each believe that the other is in love with him/her. It is this "noting" that changes the behaviors and attitudes of the two proud, stubborn characters towards the other. Another example of "noting" is when Claudio "notes" the supposed infidelity of his intended, Hero. There is certainly "much ado" made about this noting because Claudio denounces the innocent Hero on their wedding day.
Well I think there are a number of ways to look at the title. for example, it could be interpreted as Hero's actions. Because she has done nothing yet the whole dark side of the plot can be taken that she has. If that makes sense. also you could look at it as a sexual pun that often occured in shakespearen plays, with a much ado about a 'no thing' refering to genitalia. another reason could be taken as 'noting' and the eves dropping and note taking that occurs...thats only my opinion but hope it helps