Heads up, if you're an American going to Europe, be aware that attitudes to living on credit or via credit cards are at times very different.
In Belgium and the Netherlands, it's not usual to see supermarkets even taking credit cards, and some restaurants (!) don't either. This is changing, but slowly.
Conversely, good luck buying gas from an automatic pump if you're in the US and paying with a European card. In the absence of a PIN they'll ask for a ZIP code, which you don't have.
As a Brit in NY, when I swipe my UK card to by a Metro pass I'm asked for my ZIP code. I just put in the ZIP code of my apartment and have never had any trouble. A teller at the bank told me that since it isn't a US card they ignore it anyway...
I was once told travelling in the US on a Canadian credit card to just input '00000' and that it should do the trick on all of the self-serve pumps. Worked for me on multiple pumps.
Credit cards are also not so popular in Germany. Supermarkets accept the local bank debit card, but I typically leave my Visa to home.
Usually I remember to get enough money from ATM's. The worst day to forget to withdraw some cash is the first of May, when it's a bit different because all the ATM's are closed to prevent the protesters from breaking them.
I live in Belgium and all supermarkets I know of take credit cards. Maybe we don't agree on the definition of supermarket (to me it means something like Wal-Mart; in Belgium: Carrefour, Champion, Colruyt, ...), but I'll say that if it has a parking, then it most probably takes credit cards.
In Belgium and the Netherlands, it's not usual to see supermarkets even taking credit cards, and some restaurants (!) don't either. This is changing, but slowly.