Finite or non-finite?

[Ubiraci]

Dear teacher,

Is "found" in this sentence finite or non-finite?
We found him lying by the roadside and were almost sure at first that he was dead.

What is the best way to know for sure if a verb is finite or non-finite?

Thanks a lot for your help.

[Casiopea]

Welcome, ubiraci.

Every sentences must have a subject and a finite verb. Find the subject and the finite verb should be right next to it, unless there's an adverb between the two. For example,

EX: They really like swimming.
=> "They" is the subject
=> "really" is an adverb
=> "like" is a finite verb.
=> "swimming" is a noun, a gerund.

Sentence [1]
We found him lying by the roadside.
=> subject: "We"
=> "found" <finite verb>

Sentence [2]
and (we) were almost sure at first
=> Subject: omitted (we)
=> "were" <finite verb>

Sentence [3]
that he was dead.
=> Subject: "he"
=> "was" <finite verb>