In my story - Proactive Reincarnation, someone caught me with a its/it's error. They didn't remember where it was but it was easy to find. I told Open Office to find all occurances of its and it's and read them to make sure they were correct. While doing that I also decided to check for to, too, two and there, their, the're, they're. I thnk MS word can be set to flag you on some of these words but I don't use it. So my question is what other groups of words like these should i (and all of us) check for before submitting a story.

What other things do you check for before submitting a story.