Linking verbs are the opposite of action verbs; they don’t create any movement or action, but they connect the subject to the subject complement. (A subject complement adds more information about the subject.)
Look for the verb in the sentence. If you can’t actually do the action, it’s probably a linking verb.
The soup smells good. (linking verb)
I smell something good. (action verb)
I am tired.
To be is a linking verb. In this sentence, it connects I with tired.
The child became cranky just before supper.
The happy woman felt like dancing.
Seeming happy, the boy walked home with his new puppy.
Seeming is the linking verb, as it links happiness to the boy who is walking with his puppy.