As far as saving, we put a little away each month (shifting it from checking to savings), and don't book a WDW trip until we have enough to pay it off in full almost immediately. (It's a matter of personal preference: we just like to pay up-front.) In the meantime, we shrug off the desire to make non-essential purchases with the reminder that "we're saving for Disney... do you want that sweater now, or wouldn't you rather have an extra table service meal on vacation?"
For my family of four, our Disney trips are made up of 4 almost-equal cost components, each ranging around $1,000-$1,500: tickets, room, food and airfare. We can literally cut those costs in half by going during a "free dining" promotion (admittedly, we haven't timed it right yet to take advantage of that, but we'll keep trying!), and by flying for free. (We also save money on our room by traveling during lower pricing seasons).
The way we fly for [almost] free is simple: I have a JetBlue Amex card (you can get one for virtually any airline, but compare them first) which I use for practically everything I buy, all month-long. Then I pay it off in full every month, so there are never any interest charges. Every 2 years or so, I earn enough points for the four of us to fly for free. So for the $80 I'll have paid in $40 annual fees on the card, I'm getting $1,200 worth of airfare for trips to WDW every 2 years.