One of my five gold rules of good writing is to be correct. I mention it a couple times. The gist is that you need to get your mechanics (grammar, spelling, punctuation, syntax) correct; the other is that your facts have to be true. (I tell people that as a tech writer, I tell the truth for a living.)
I just ran into an excellent essay on this subject. Here’s the incorrectness that triggered the essay:
Click the link under the picture. What he says is exactly my point about correctness. The sentence is not quite true. Some of you, no doubt, will be able to figure out that the inaccuracy is; it’s subtle. (And I’m not referring to the use of “which,” which should be “that.” —that’s an error in mechanics.)
So. Be sure you get your facts right. Tell the truth.