It's vs. Its

I've never had a problem using these two properly. NEVER. It's one of the things that makes me special.

If you have difficulty remembering the difference just think of it like this.
If 'He' possesses something we attach the 's' to the pronoun to make 'his', as in 'his book'.
If he is something, we'd use the apostophe, as in 'he's angry'.
It's never: 'his angry' or 'he's book'. 'He's angry' and 'his book'.
(9__9)
In the same manner, the 's' attaches to the 'it' when in the possessive case and just rides along with the apostrophe when used in a contraction.