"What happens if I mispronounce a name while casting a circle?"
Well, if it is a bad mispronounciation, then you will immediately be struck dead by lightning. Just kidding. Nothing is going to happen to you. The best thing to do in this situation is to laugh, forget it, and move on. The gods know that part of being human is making mistakes. That's what makes our lives so interesting, isn't it.
The same thing applies to forgetting to do something. Simply stick it in when you remember it, if it makes sense. Of course, if you are closing your circle before you even cast it, the you should read the ritual a little more carefully next time.