A predicate nominative is a word that renames the subject of a sentence. It is found after the linking verb in the predicate of the sentence. A predicate nominative is also called a predicate noun because it is always a noun. To find the predicate nominative, find the word after the linking verb that can replace the subject.
First, find the subject of the sentence, the noun that the sentence is about. Consider this sentence: "Mr. Johnson was my teacher." In this case, the subject is "Mr. Johnson." Next, locate the linking verb. Linking verbs include the state-of-being verbs am, is, are, was, were, being and been. The linking verb in this sentence is "was." Finally, find the noun in the predicate that renames the subject. The predicate is the part of the sentence that includes the verb and all of the words that follow the verb. In this case, the noun in the predicate is "teacher." "Teacher" is the predicate nominative. To check for accuracy, flip the subject and predicate. "My teacher was Mr. Johnson." If they can be flipped, because they are the same person or thing, you have correctly identified the predicate nominative.