No one likes waiting on line, especially when it seems like everyone else's line is moving faster. If you have to choose a direction — left or right — you might have better luck going to the left, where lines tend to be shorter.
I read this tip on several forums and guidebooks to surviving notoriously long lines at theme parks, including this Woman's Day article. The theory is that left lines tend to be shorter because the majority of people are right-handed and tend to unconsciously choose things on the right. We do that when choosing movie theatre seats and when shopping.
Of course, other factors will play into how fast a line moves and how many people are on it, including how many items each person has (in a checkout line) and superstition, but, all other things being equal, try going against the grain and veer left instead of right.
Picture: Random Retail/Flickr