Does anyone know how to determine the subject, verb, direct object or complement in a sentence?

Subject - person or thing about whom the statement is made, before verb

April cooked apples.

(April is the subject)

Verb - the action

(Of the previous sentence, cooked is the verb)

Direct Object - answers

whom? or what?

(Cooked what? She cooked apples.)

Complement - completes the meaning of the sentence

John is weak

(Weak is the complement)