The basic steps when constructing a correct sentence where the Subject and the Verb Agree are :

1 – Identify your subject.

For example, Joe’s sister’s dog is really friendly. In this case, the subject is not Joe or his sister. It’s the dog we are talking about.

2 – Is your subject singular, plural or collective?

Singular: The dog is friendly.

Plural: The dogs are friendly.

Collective: Class 5A is waiting for the teacher to enter.

3 – Use the right verb form (or conjugation) for your Subject.

I start, you start, he/she starts, they start, we start, it starts.

Let’s look at collective nouns closer.

Collective Nouns are ways of talking about many things as ONE. For example, a fleet of buses, a box of crayons, collection of stamps, choir, herd, tribe etc. Maybe 1 fleet has 20 buses, 1 box has 20 pencils and a collection has 20 stamps. A choir has many people and a herd contains many goats, for example.

A box of crayons costs $10. 2 boxes of crayons cost $20.
The fleet of buses operates from 7am to 11pm daily. Outside these operating times, the fleet rests in the bus depot.

Everyone, Everybody, No one

Everyone wears a mask these days, but not everybody likes it. No one knows when they can remove the masks and walk around normally.

In the examples above, we are referring to a group of people with the same attitude, desires and actions. So, we can consider them as a singular entity,

In the case of ”police”, you can treat the word as plural or singular.

Police is looking for a suspect from last night’s incident. Police are looking for a suspect from last night’s incident.