Scout out ATM fees
Some people like to be all 21st-century cool and say, "Oh, I NEVER carry cash." Which not only pisses off valets, bellhops, and Christmas party bartenders who never get tipped; it also makes it tough to hand a quick $50 to that little cousin you totally forgot to buy a present for. It's a fact of life that ATMs become all the more necessary when we travel around the holidays.
Smart travelers look and see which in-network ATMs their bank partners with. Those may be obvious as the ones in front of the grocery store, or at a local credit union. If you have a national bank, make note of where its ATMs are in the city you’re visiting. And if your bank is local, it will likely still have partner ATMs that don't charge fees.
Lock in low foreign transaction fees
Because you can't put a price on the joy on a small child's face, December can be an occasion for taking on new credit cards. Questionable financial responsibility aside, the applications are where you want to watch for foreign transaction fees, among others. Credit cards are generally considered a wise move when spending overseas since they give you the best exchange rate. But fees of 2% to 3% often negate any savings. Doesn't sound like much, but if you pay for hotels, meals, and "I Heart Paris" T-shirts with plastic, that can mean $100 or so you're flushing away. Or, like, 15 "I Heart Paris" T-shirts.