The confusion between it’s and its occurs because on virtually every other word ('s) indicates possession, so English speakers naturally want to use it’s to mean “something belonging to it.” But it’s is only used when it’s a contraction of it is or it has.
The ironclad rule - no exceptions - is that if you can replace the word with “it is” or “it has,” use it’s. Otherwise, it’s always its.
Two simple tests
If you can replace it’s in your sentence with “it is” or “it has”, then your word is it’s; otherwise, your word is its.
Its is the neuter version of his and her. Try plugging her into your sentence where you think its belongs. If the sentence still works grammatically (if not logically) then your word is indeed its.
After keeping us waiting for a century, the great American writer reveals all.
Mark Twain left instructions not to publish his autobiography until 100 years after his death, which is now.
Exactly a century after rumours of his death turned out to be entirely accurate, one of Mark Twain’s dying wishes is at last coming true: an extensive, outspoken and revelatory autobiography which he devoted the last decade of his life to writing is finally going to be published.
The National’s 2007 album, Boxer, established them as the overlords of Brooklyn’s music scene. With a hauntingly beautiful new album, High Violet, and sold-out shows in New York’s Radio City and London’s Royal Albert Hall, are the National poised to be the American answer to Radiohead?
I haven’t any right to criticize books, and I don’t do it except when I hate them. I often want to criticize Jane Austen, but her books madden me so that I can’t conceal my frenzy from the reader; and therefore I have to stop every time I begin. Every time I read ‘Pride and Prejudice,’ I want to dig her up and hit her over the skull with her own shin-bone.