We always shake hands with our right hand because of a couple of reasons. One reason is because it comes from a time when people used to their hands to clean themselves after using the restroom. If you were to shake someones hand you would want to use your right hand. Shaking with the right hand was friendship and the left hand was considered to be an insult. In Europe, when people carried a sword it would show friendly intentions if you raised your right hand because the weapon would not be in the right hand.