Timing is everything...especially when buying your airline tickets. When do you buy them?
The rule of thumb is to purchase your tickets between three months and 14 days prior to domestic travel. Why? Airlines don't usually start releasing cheaper seats until three to four months before departure for domestic travel. For international travel, try four to five months out.
You may find last minute specials for off peak travel such as round trips from Thursday to Monday or Saturday to Tuesday. If you can be flexible, check out days on one side or the other of your original flight days. It may save some money.