The further out you can book your flight, the better chance you have of getting a good deal. Sometimes booking as far as six months out will save you a significant amount of money.
Airlines typically will put out their sales fares on Monday evening, with the other airlines matching the prices by Tuesday morning. They then pull their sales on Thursday nights, so you only have a few days to get those discount fares.
If possible, it's always best to try and fly in the middle of the week. Business travelers tend to travel more on Mondays and Fridays. The other days are then discounted due to supply and demand. Also, if you can fly in the middle of the day, instead of in the morning, you are once again, going to be avoiding the rush times, and saving yourself some money.
