I did a fair amount of research before buying anything for our upcoming, first international trip. I felt pretty prepared! However...
One piece of advice I dismissed was to open a credit card that has NO foreign transaction or international fees.
I bought airline tickets through Condor Air (a German airline) for our return flight, and was shocked to see a $60-something "foreign transaction fee" on my credit card account a day or so later. A couple of other small-amount tickets for museums, tours, etc. that I purchased online also rendered similar small percent fees to my account afterward.
I read that credit unions often do not charge international fees. I had my husband check with his credit union to see if they charge international fees. Yep, they do. So I checked another big credit union in our area, and they have no annual fee, no international fee. A Google search will help you find other big name banks who offer no international fees, if you don't have luck with the credit unions in your area.
I will use my new credit union card for finalizing our payments at our hotels, eating out, and other expenses, so as not to incur additional fees that will add up over our trip.