People! There is nothing morally or politically wrong with poor grammar, but it makes for distracting reading. Keep this simple rule in mind, and those of us more grammar-sensitive will breathe a sigh of relief:
"It's" means "It Is." Only use the contraction It's when you mean "It is."
"Its" is the correct word when you want to indicate possession—as in, "its own best friend."
If you ask the question, "Do I mean 'it is'?" whenever you type 'it's', you will make many people happy.
I know this doesn't rise to the level of importance that wars of aggression, unconstitutional behavior by government officials, or the world economic crisis do, but here's a small problem you can immediately correct! And from here, we can take on the bigger issues with one less distraction. It's that simple. (Yes: it is.)
It's totally understandable that the it's/its confusion exists: for all other words, you do use the apostrophe to indicate possession (e.g., "Dave's silly obsession") as well as to contract "is" (e.g., "Dave's a silly person"). "It's" is an exception: it only ever means "it is." If you employ the simple rule above, you'll get it right every time.
Of course, I'm only a physical therapist by profession. Any professional grammarians out there who want to correct/augment/clarify this? Please comment! Thanks (no, not "thank's"—we can get into the misuse of apostrophes for pluralizing some other time) for listening!