Pay cash. For some reason, it's harder for people psychologically to part with their cash than it is to swipe a card. Maybe it's the act of physically seeing the money change hands, or maybe it's because you don't want to break a $20 for a $2 cup of coffee.

Money 911: Your Most Pressing Money Questions Answered, Your Money Emergencies Solved (ed. Harper Collins, 2009) - ISBN: 9780061962097