Before traveling abroad, credit card companies suggest you give them a call. After all, who wants a waiter telling you your card has been declined...when in reality your credit card company is just protecting you?
It's also a good idea to check your credit cards' expiration dates. If the date is close, give them a call to request a new one sooner. Some companies cut those dates pretty close. While you're at it, ask the company what is the best number to get a hold of them once outside the US. It's a good bet the 800 number on the back won't work after you leave the US. You could always put that number in your cell phone so you have it. Just list it under something you will remember and not the credit card company name.
Don't forget to save your receipts. You will probably never need them, but it's better to have them. If your bill looks high, you can always double check it against your receipts.
Did you know that many countries are switching to "chip and PIN' technology instead of the magnetic strip on the back of the card? With that in mind, some vending spots may not recognize the magnetic strip or they may have a minimum purchase on the transaction.
Solution...always carry some cash. You won't need much but some is definitely a good idea.