I’m not the first person that you’d think of to ask a grammatical question, but I do a lot of writing and correct grammar is important. Better to let the world think you’re ignorant than to put it in writing and remove all doubt, right?
So, for my own reference, here’s the rule for apostrophes with the word ‘it’:
Use an apostrophe with the word "it" only when you want to indicate a contraction for "it is" or "it has." Its is a pronoun, and pronouns have their own possessive form that does not use an apostrophe. For example, "That noise? It's just the dog eating its bone." This may seem confusing, but it follows the same pattern as other possessive pronouns: his, hers, its, yours, ours, theirs.