Thank you to Bill Ward of the Minneapolis Star Tribune for keeping the importance of manners in the forefront in today's article, "Mind Your Manners." In it he highlights segments from the book, How To Behave: A Guide to Modern Manners, by Caroline Tiger. The book is on my to read list.
The update I make to a suggestion in the article is that when the person in line ahead of you tries to get 22 items through the 10 item only lane, to begin counting off the item number would be equally as rude. Rather, a statement such as "You must not have realized that this is the line for 10 or fewer items" if the cashier has not yet realized this; it is the cashier who is responsible for monitoring the flow of the lane and directing this person to the appropriate lane.
I also suggest avoiding name calling (even in your mind) such as "bozo" or other terms. Sometimes, people really are clueless. Give them the benefit of the doubt, just as you would want for yourself.