How much money will I need to bring?
The easiest way to budget for traveling abroad is to track your spending habits at home for a few months before you leave. Depending on what is included on your trip, you should consider the fact that you will spend at least 2 times as much than you would at home when you travel to countries in Western Europe. Things like toiletries, electrical appliances (ie. hairdryer, curling iron, etc.), food and beverages tend to be much more expensive than they are in most places in the U.S.
Here's an article about what you should know about budgeting for your trip abroad.
Cash, traveler's checks, credit cards... what's the best option?
The best way to get cash is through withdrawals from ATM machines in abroad. This generally ensures the best exchange rate and you avoid the hassle of exchanging traveler's checks and the danger of carrying around a lot of cash.
It is always wise to have a credit card just in case you see something you just have to buy. It is also important to inform your bank and credit card companies of your travel plans and dates as it will avoid theft suspicions.
Other helpful international resources: