My two AP Style pointers.. I hope it is my turn. I decided not to check before I posted this.
these are also from a website that has the rules explained by a journalist or teacher, can't remember I wrote it down in a notebook somewhere.
1.it's, its -- "It's" is a contraction that means it is, or it has. "Its" means "belonging to it." Whenever you must choose one or another in a sentence, try inserting the phrase "it is" or "it has." If one of those pairs makes sense, then use it's. I use funny word associations to remember things like this. Technically, they are called mnemonic devices (as in the movie, Johnny Mnemonic). When I see the word "it's," I tell myself "the apostrophe means 'to be.'")
2.lay, lie -- Not as tricky as it might seem. The way I remember the difference is that "lay," in the present tense, requires an object; in other words (pardon me) you can only "lay" something. The word "lie" in the present tense means recline on a horizontal plane. Examples in the present tense: I lay the book on the table. Now it lies there. In the past tense, lay becomes laid, and lie becomes lay. Examples: I laid the book on the table yesterday. It lay there for several hours before my brother picked it up.
