Regarding credit cards: be aware that Discover/Novus cards are not accepted in Spain. Be sure to bring Visa and/or MasterCard.

As for cash, use your ATM card as much as possible. It'll usually get you a better dollars/euros exchange rate than the money changing businesses offer. But remember that you'll be charged a service fee each time you take out money, so be sure to withdraw a couple of days' worth at a time.

Buen viaje!

best way to get money out that I found while travelling and studying abroad saves you tons of fees. Since you are in teh states I am guessing that you have a basic checking account that also gives you access to a Visa or MC debit/check card. If you have one of those, you can take the card into the bank and ask for a cash advance (like you would on a credit card) but because the money is coming out of a check card there are no percentage fees imposed. So you ask for $100 USD in local currency and you get say $100 Euro's (to make the numbers simple) now when you get your bank statement it is possible that with the currency rates (favorable for big transactioners such as Visa, MC or banks) you have a withdrawl of $97 instead of $100 and you got $100 Euros for it.

Worked wonders for me I totalled out that I saved compared to some of my friends studying abroad with me over $150. That is a great weekend trip.

My only other tips to you in additon to what others have posted is to make sure to get yourself out and go even when you dont want to (and there will be times when you dont). Take as much advantage of having a local base and travel around Spain and Europe. Take tons of pictures instead of buying touristy things (they are the most valuable thing to me) and of course enjoy yourself!