HOW TO USE THE WORD "FACT" PROPERLY

Almost never.

Whenever you're about to say it or write it down, make sure that you're not talking about something else. Generally, the word "fact" should be replaced by the phrase "my personal interpretation of an anecdote or something I saw on TV". Sure, it's a mouthful; it doesn't roll off the tongue as easily. But maybe, you're only thinking of something as a "fact" because you have not been sufficiently exposed to other peoples' different perspectives on it.

An even better solution is to replace it with "I think". Here are two statements to illustrate my point.
- It is a fact that Donald Trump is racist. .
- I think that Donald Trump is racist.
I would argue that the second statement is preferable for a few reasons. First, it's actually more persuasive. You're explicitely stating that you're thinking; you're not just spewing out something you got from somewhere, you actually thought about it. Second of all, it's more inviting for another person to engage conversation. There's an implicit "What do YOU think?" at the end of that second statement. Not only are you sounding less authoritarian, but you also increase your chance of learning something.

The word "fact" should be reserved for boring things like....facts. Like the Earth is round and stuff. And even that can be questioned.