Cash vs Credit Card

For most things credit cards are fine though best to use Mastercard or Visa, not American Express which is less widely accepted.

You will want cash, but you don't need to take any from home. ATMs are everywhere, including at the airport. Rule of thumb: use a credit card for major purchases and use a debit card linked to your checking account to get cash from ATMs for everything else. Be sure to notify your credit card providers and your bank that you will be in Europe. If you don't, a computer is likely to freeze your accounts for what it recognizes as unusual--and therefore possibly fraudulent--use. Read this helpful article by Rick Steves.

Most credit card companies,Capital One is an exception,will charge you a certain percentage "foreign transaction fee" which can amount to several dollars on large purchases such as hotels and car rental. Check with your issuing company.