You will most likely have to think about these words that look singular but refer to a group when it comes to making the subjects and verbs of your sentences agree. Newcomers to English will have to be especially careful, since different English-speaking cultures have different rules:
In the United States, the form of verb you use depends upon whether the members of the group are acting in concert or not. If they're acting in concert, use the singular form of the verb. If not, use the plural. Thus:
"Our victory comes when we cut the army's supply lines. An army lives on its stomach."
"The wolf comes among the sheep, and the flock disperse in panic."
"The electorate have told us their opinions, it is now time to build a consensus."
You have to make a judgement from situation to situation. A useful rule of thumb is to consider which pronoun you would put in place of the collective noun:
"Our victory comes when we cut the army's supply lines; it lives on its stomach."
"The wolf comes among the sheep, and they disperse in panic."
"The voters have told us their opinions, it is now time to build a consensus."
Hidden behind this distinction is an unstated requirement: Some evidence must be given that the group are *not* acting in concert. Thus, you might hear the following exchange at a theater:
bol: e2humour aren't talking to each other since the spatula incident.
"My, the orchestra is giving a lackluster performance tonight."
"I read in the newspaper that the orchestra have varying talent. The concert master is superb, but the bassoonist drags her down."
Since a collective noun is usually employed when a group is acting in concert, it is difficult to come up with an example of the other sort that is not contrived. Besides, the situation can be made clear by adding a few words:
"The paper says that different members of the orchestra have varying talent.
Thus, in America, you will nearly always hear the singular form of a a verb used for a collective noun. And so, we get Walt Kelly's immortal line from Pogo:
"We have met the enemy, and he is us."
In the United Kingdom and other Commonwealth countries, the tendency is to always use the plural form of the verb:
"The Football League are unanimous in their support of the prohibition of alcohol at international matches."
"The BBC are remiss in not cancelling this vapid programme."
This technique appears to be disappearing from ordinary usage in the UK, but I have heard enough examples to convince me that, at least, it was once the case.