We save and pay cash. Well, we actually use credit cards in most situations but we pay the balance at the end of that month with the cash saved for the trip.
"Vacation" is a line item in our budget. But vacation is at the bottom of our budget because everything else is more important. Before vacation comes retirement savings, taxable savings, all monthly bills (we have no debt, so this would be utilities, cable, phone and insurance payments), groceries, money for nephew's college tuition (ends in two years), dog fund (for food, grooming, vet visits and dog medication), monthly discretionary spending and "mini-emergency fund" (for all that little stuff that pops up throughout the year. We have a larger emergency fund that is only touched for a big emergency, like a job loss. We also used to have a "future car fund" in our budget, but that is fully funded now.
Those savings goals and other line items are worked out first, what is left over is our vacation fund. This year there's enough for two weeks in Italy, so a pricey vacation. Next year we'd like to do some things around the house and so we'll probably stay in the states and do something cheaper for vacation and use the remainder of that money for the work around the house.
The whole key is living beneath your means. But remember, no matter what, you need that emergency fund. And retirement savings has to come before vacation savings!