A verb should agree with the noun that is its antecedent.
Note that “audience,” “neither,” “each,” and “either” are singular and require singular verbs; “both” is plural and requires a plural verb.
Shakespeare’s audience was [sg.] often loud and unruly.
Neither Juliet nor Helena hesitates [sg.] to declare her love.
Both Juliet and Helena boldly declare [pl.] their love.
Both [of the twins] have [pl.] a servant named Dromio.
Each Dromio, mistaken for the other Dromio, receives [sg.] a beating for his apparent error.
Agreement Errors Spotted in Scholarly Writing:
This carnivalesque inversion of teacher and student imply that someone must always be the teacher and someone else the student and ultimately reinforce the hierarchical nature of traditional training. [This agreement error occurred in a draft of my own writing. I introduced the error when I edited the sentence and change the subject to the singular “inversion” but didn’t change the subsequent verbs. To fix the sentence, change “imply” and “reinforce” to “implies” and “reinforces.” Lesson: CHECK your n-v agreement AFTER MAKING SENTENCE-LEVEL REVISIONS.]