Finite/non-finite verbs

A friend and I are really struggling to understand finite and non-finite verbs! Is there an easy way to remember the rules about them?

[Casiopea]

Welcome, E x.

Here's a rule of thumb: if there are two verbs in a row, the first verb is the main verb (finite) and the second verb is non-finite.

EX: I walked. <1 verb: "walked" is a finite verb>
EX: I had walked. <2 verbs: "walked" is a non-finite verb; it's a past participle>

Finite verbs agree in person and number with the subject,

EX: She walks. <present tense>

Non-finite verbs are not connected to the subject. They are objects of the main verb,

EX: It has to work.
<modal + non-finite verb; "work" is connected to the verb "has to", not to the subject>

EX: I am supposed to go.
<be + adjective + non-finite verb; "to go" is connected to "be supposed", not to the subject>

Again, when in doubt, count the number of verbs. If there are two verbs, the first agrees in person and number with the subject (finite), the second does not (non-finite).