"It's" is a contraction for "it Is. It's always a good idea to wear matching socks.
"Its" is the possessive form of "It." Although the peach was gigantic, its pit was rather small.
Hint #1: Whenever you see an apostrophe with "its," read the apostrophe as an "i."
So, if the sentence reads, "Although the peach was gigantic, it's pit was rather small,"
you could try reading "it's" as "it is" and see if the sentence makes sense. It doesn't,
so you know that the apostrophe is incorrect.
Hint #2: Learn the difference between "it's" and "its." This error drives professors