Pronouns have to agree in person, number and gender with the words they refer to (called their antecedents). (For basic guidelines on pronoun agreement, see Pronouns have to agree.) But when singular collective nouns are used as antecedents, it can be difficult to decide whether you need to use a singular or plural pronoun.
A collective noun names something that has many members or parts. Some common examples referring to groups of people are cast, committee, club, company, group, staff and team. Because these nouns include many members, they may have a plural meaning even when they are singular in form. Use these guidelines to decide on pronoun agreement.
If the members of the group are acting as a unit, the noun will be singular and will take a singular pronoun:
The staff has achieved its goal of collecting $5,000 in the marathon.
The cast will present its final performance Sunday evening.
If the members are acting individually, the noun has a plural meaning and will take a plural pronoun:
The staff have submitted their reports.
The cast tried on their costumes before the dress rehearsal.
Hint: Plural meaning is often indicated by the presence of plural nouns (like reports and costumes in the examples above).