The Three Tests
The Noun Test
A verb that functions as a noun (a subject, a complement, or the object of a preposition) is not a finite verb. (Do not underline it twice.)
The "To" Test
A finite verb phrase cannot begin with "to." Thus in "Bob went to his room to do his homework," "to do" is not a finite verb. (Do not underline it twice.)
The last way to distinguish finite verbs from verbals is the simple sentence test. If you are not sure about whether or not to underline a verb twice:
1. Find the subject of that verb.