Are group nouns like team or police singular or plural?
The team (is/are ) preparing for the next game.
Police (is/are ) looking for the suspects.
Group nouns are a bit tricky in English. We call them "collective nouns,"* as they usually represent plural quantities. "Team" is a collective noun, as it represents a group of people. However, "team" is singular**, as there can be more than one team (teams). The singular form of "to be" for this situation would be "is." "Police," although it is also a collective noun, it defaults to "are,"since there is no widely used plural form.
In summary, here's a checklist*** for dealing with words that might be collective nouns:
*Not to be confused with mass nouns, which are nouns that can't have plurals (often because they can't be counted). Ex. happiness, china (the dishware), furniture
**As a commenter noted, there may be a difference in British English. I am writing from the perspective of American English.
***If you have a way to improve this checklist (I was a bit tired when I wrote this), feel free to comment your suggestions!