Anyone who follows this blog knows I’m not big on rules of writing. But in my experience as an author, a reader, and an editor, I’ve found the word "that" is one of the least needed, most overused, and most frequently misused, in all of modern literature.
To better understand what I’m driving at here, allow me to rewrite those first two lines with the "thats" left in:
Anyone who follows this blog knows that I’m not big on rules of writing. But in my experience as an author, a reader, and an editor, I’ve found that the word "that" is one of the least-needed, that it is among the most overused and misused words, in all of modern literature.
Notice how the "thats" add nothing to the passage. They don’t clarify, they don’t improve flow, and they don’t reflect any sort of stylistic choice, either. They’re just taking up space and bloating word count. The word "that" is only rarely actually needed in a sentence, but for some reason, an awful lot of writers are in the (bad) habit of peppering their prose with this largely superfluous word. Consider the following, typical constructions:
He knew that I wasn’t going away.
He knew I wasn’t going away.
She was sure that everything would be fine.
She was sure everything would be fine.
You get the idea. When you find yourself tempted to include a "that" in a sentence immediately following a verb or adjective, try the sentence without the "that" first. In the vast majority of cases, you’ll find your meaning is perfectly clear, and your prose much tighter, without it. Now look at these constructions:
None of the cars that we saw were suitable.
None of the cars we saw were suitable.
The books that I needed weren’t in stock.
The books I needed weren’t in stock.
Again, the "that" adds nothing but characters on the page. As with "thats" following a verb or adjective, try any sentence where a "that" follows a noun without the "that", and see if it doesn’t read tighter.
So when is it appropriate to use "that"? When it’s needed to clarify your meaning:
As a pronoun – That is the hotel where we stayed last time we were here.
As an adjective – I’m pretty sure that book belongs to Jimmy.
Or to improve the flow of your prose, as a stylistic choice:
As an adverb – It didn’t matter all that much.
(compare this to)
It didn’t matter much.
Moving on, what about "that" versus "who"?
The judge that heard the case was biased.
The judge who heard the case was biased.
All the kids that came to the party had a good time.
All the kids who came to the party had a good time.
Presumably, the judge is a person, not a thing. Kids are people, too. People are "whos", not "thats". However, both of these examples illustrate the case where a relative clause requires an object to restrict an antecedent, which is just a fancy-pants grammarian way of saying a "that" or "who" really is needed to clarify the meaning of the sentence and make it grammatically correct. Just be sure to use "who" in reference to people, and "that" in reference to things.
One more thing: are you mixing up your "whiches" with your "thats"? Consider:
The dog that was found in her yard was a stray.
The dog, which was found in her yard, was a stray.