he makes them -are the best. / Joe's going to have to buy some more patties soon = Joe is going to have to buy some more patties soon. However, 's is never used to indicate possession in pronouns. We do not write hi's (instead of his), for example. Here is a test you can perform to determine whether to use it's or its: Replace it with his and see if the sentence still makes (grammatical) sense. "His a common mistake" does not make sense. However, "The boat has a hole in his hull" does make sense - at least grammatically (of course boats are not boys, but we can pretend that they are for the sake of improving our spelling). The rule to apply, then, is this: If the sentence makes sense with his, which does not have an apostrophe, it is safe to replace it with its, which also does not have an apostrophe.