Yes, I said it, on social media, under my own name as an editor: "Half my editing is inserting 'that' where journalists have left it out."
Yes, a jocular exaggeration, but it smoked out the that-cutters, the writers, journalists, and, Fowler save us, editors who see it as their duty to excise that wherever it appears as a conjunction.* Some of the that-cutters profess their fealty to the Associated Press. So let me show you what the Associated Press Stylebook actually says:
Use the conjunction that to introduce a dependent clause if the sentence sounds or looks awkward without it. There are no hard-and-fast rules, but in general:
–That usually may be omitted when a dependent clause immediately follows a form of the verb to say: The president said he had signed the bill.
–That should be used when a time element intervenes between the verb and the dependent clause: The president said Monday that he had signed the bill.
–That usually is necessary after some verbs. They include: advocate, assert, contend, declare, estimate, make clear, point out, propose and state.
–That is required before subordinate clauses beginning with conjunctions such as, after, although, because, before, in addition to, until and while: Haldeman said that after he learned of Nixon's intention to resign, he sought pardons for all connected with Watergate.
When in doubt, include that. Omission can hurt. Inclusion never does.
Got that?
To enlarge on that a little. Omitting that is common and acceptable when there are a couple of short clauses, as in She told him it was over. But you really ought to use that when you have more than one clause in the predicate, as an act of simple, decent respect for the reader: She told him that it was over and that she would call the police if she ever heard from him again.
* That post also smoked out those people who think that that as a relative pronoun cannot refer to human beings. Their lack of awareness of that use of the pronoun regularly in English for the past 13 centuries is regrettable, but I can address the point if you need help.
