I must confess that I haven’t watched a StrongBad email in a long time (possibly three years) I look forward to a day or two spent catching up on the archives. But StrongBad has been indelibly itched into my psyche whenever I’m trying to decide where to use apostrophes… particularly in the case of its v it’s.
Here’s a little song that will help you remember that when its is possessive it’s just i-t-s and when it’s a contraction it’s “i-t apostrophe s”.
That’s from this little collection of grammar songs.
I think I’ve posted this before (some time ago) – but it continues to be useful.