Greetings/Parting Company
Generally, when people who are not well acquainted with each other meet or part company, it is considered polite to shake hands. Refusing to shake an offered hand is likely to be interpreted as rude. When shaking hands, a firm but not tight grip is prefered. Simply placing your hand in the hand of the other person is considered to be an ill mannered and insincere handshake. Also, kissing the cheek of an American is may take them off-guard and lead to major ackwardness.