We get APs, DDE card, golf card, and we go twice within 12 months. That way, the bulk of the second trip is already paid for. We just have to get there. We eat breakfast and sometimes lunch in the villa. And we only occassionally do the signature type meals. (We've found they aren't usually worth the price. We can do better at home.)
And (THE biggie) we don't buy a bunch of expensive Disney stuff while we're there. We've found that all the "stuff" in the shops can be the real price breaker on vacations. Bring sweatshirts, ponchos, sunglasses etc., don't buy them from Disney. Bring golf hats and balls from home, don't buy them at the pro shop. Buy princess outfits or other costumes before you arrive - the prices in the parks are HIGH. Buying loads of stuff on site can easily double the cost of a trip.
We also don't do fireworks/Illuminations cruises or most of the other expensive add-ons. We've done them in the past. We're just as happy watching the shows in the parks.
Eating even a couple of evening meals in your villa can save a bunch. TS meals are nice, we enjoy them too, but a TS meal every night can add up fast. And watch out for "adult beverages". The prices are inflated. Like many folks, we enjoy a drink before dinner, but buy that whole bottle of wine or 6 pack of beer off site and enjoy it back in the villa. Even with the DDE discount, alcohol in the restaurants and bars can really spike the bill upwards.
We don't feel like we're missing anything by doing all this, and we get to enjoy WDW more often. We're now thinking about moving from two trips a year to three.
DisFlan