It's its!

It's a shame that the English language has had its writers in the current generation so poorly trained as to confuse the usage of "its" and "it's". Since I recently had to retrain my well-educated partner, via much repetition, to use them properly, and since I've seen such misuse this morning in two articles written by otherwise intelligent people: here is the proper usage of "its" and "it's".

"its" is a possessive pronoun.
"it's" is a contraction of "it is".

See the first sentence of this post for an example of correct usage. Anywhere you see "it's" (with apostrophe), mentally replace it with "it is". Do that several times and you'll start to cringe when you see the wrong usage, just like I do.