know + noun/pronoun
I know the answer.

know + about + noun
I knew about the problem.

know + of + noun
I know of someone who can help you.

know + noun/pronoun + to be + noun
I know him to be an honest man.

know + noun/pronoun + as + noun
I knew him as a friendly person.

know + clause
I know what you mean.

know + that + clause
I knew that something was wrong.