Determine the subject of your sentence. The subject is the object that is doing the action or is in a state of existence or being. It is the who or what of your sentence. It may also be a pronoun, which takes the place of a noun, such as "he," "she," "they" or "it."
Determine if the subject is engaged in action or in a state of being. The sentence "The dog barks" has a subject, "the dog," that is engaged in action. The sentence "The dog is quiet" has a subject that is in a state of being.
Determine if the sentence requires a subject complement to further identify the subject. The sentence "The milk tastes" is not a fully defined sentence as an inanimate object cannot taste, but instead is tasted. In the sentence "The milk tastes sour," the subject is linked to its complement with the linking verb.
Complete your sentence by putting the parts in their proper order. Remember that your sentence must have a subject and a predicate. The predicate comes after the subject and can be an action or a linking verb. A linking verb requires a subject complement.