A direct object will follow a transitive verb (those verbs that "take object"). Direct objects can be noun, pronouns, phrases, or clauses. If you can identify the subject and verb in a sentence, then finding the direct object—if one exists—is easy. Just remember this simple formula:

subject + verb + what? or who? = direct object

I can't say it = IT is the object of this sentence (D.O)

I know her very well = HER: D.O

I sold my house last year = My house is the D.O

She's writing a very cool and interesting essay about plants: A very cool and interesting essay = D.O

Only transitive verbs take object. The object may take the following forms:

a) Noun: I put the cloth on the table.

b) Pronoun: I saw him yesterday.

c) Infinitive: She likes to sing.

d) Verbal noun: We heard the singing of the birds.

e) Gerund: They deslike running.

f) Phrase: He does not know how to do that.

g) Clause: I think he will come.