Carrying cash when travelling
Your 'readies' are going to be your best and worst friend when you are away. Some people unexpectedly become very careful planners while others tend to blow what money they have extremely quickly.
Cash is the ideal way to have your money in some countries as little else is accepted but be VERY careful regarding your security. It is wise to spread what you have between your bags, money belt and pouches. This way if you are the victim of theft you will hopefully not lose the lot.
Smaller denominations are also best as you are more likely to be able to get change from a $10 bill than a $50. They are also safer in case you lose them.