Earn Miles!
Charge cards attached to mileage programs are great - you'll accumulate more if you charge everything, as suggested above. Of course you have to be careful to pay it all off so you don't get hit with big interest. (If that's a potential problem, apply for a card that has a lot of initial miles and use those for your flight, but don't try to rack up the miles for future flights.)
American Airlines' Citibank cards can give you 20k or 25k miles up front, plus a free companion certificate. (Consider applying for 2 cards - one for each spouse - to double the initial awards.) 25k = a free RT in the continental US, and the companion certificate means a second person files free, so you'll only pay for 2 of the 4 (or only 1 if you've gotten 2 cards). It'll take some advance planning to get flights that have award seats available and that qualify for the companion flight, but you'll save big.
(You'll need to book directly through the airline, but first go to some of the sites suggested above for awhile to get a feel for what discount fares to your desired destination should cost, so you don't end up paying way too much for the 2 paying passengers.)
, property taxes, etc. I remind my husband that even if it is only $1, to charge it. Of couse he looks at me like I am crazy, but each year, we have been able to book four award seats to one destination. It really works 
!