I continue to see instances where it's is written when its is what is meant. I see these from people who I know do know the difference between the contraction and the possessive. Heck, I admit I have even caught myself occasionally type the apostrophe and then have to delete it. It's not as though I fail to understand how it happens.
One is focused on the idea one is expressing; one knows that when nouns are made possessive they get an apostrophe before the s; in that moment one's mind doesn't dwell on the fact that rule doesn't apply to pronouns. And while other inappropriate appending of 's to a pronoun would get flagged by spell checking (him's, her's, them's, you's, I's), those aren't even words that would come to mind; one would never type those accidentally. It's only possible with its. It's will never be flagged as misspelled, because it's not, but no software is going to identify context to know whether it's being misused (and as soon as software can do that, that will indicate they will have supplanted us as the superior intelligence).
(Ha ha. See what I did there? Eh, let's move on.)
So, until technology develops sentience and human writing becomes unnecessary (possibly because humans have become unnecessary), I have a simple way to never again accidentally write it's when one means its.
Never type the contraction it's.
It is simple enough to get by without contracting it is and typing the pronoun and verb separately. (One doesn't save that much space anyway, especially with proportional fonts.) Then one can safely type its and always be correct.
Well, okay, one will need to stop thinking the term it's first. That's probably going to be a trickier habit to break. So perhaps first one will need to unlearn that one can even contract it is. Perhaps we need to stop teaching that in school altogether. And as long as we're eliminating contracting it is, for the sake of consistency we probably need to get rid of the concept of contracting two words into a single term altogether. Then apostrophes would only apply when making nouns possessive.
Granted, then it would make more sense if all possessives used apostrophes, so we'd need to change the handling of pronouns. Theirs would become them's, his would have to change to him's, etc. (but on the upside, hers would sound the same, and only require adding the apostrophe: her's). Then its would be eliminated, leaving only it's to indicate its possessive form.
At which point, our current inclination (it's by default) will be right, without us having to change.
See? It's simple. Er... it is simple.