Buy your tickets when allowable by the airline (I agree that it's usually 11 months prior to the date of departure) and remember that if fares should drop AFTER you purchase your tickets, you should be able to get the difference refunded to you by the airline. Of course, the airline won't let you know that the fare has dropped, but it's worth it to check the fares regularly even after you buy your tickets. I haven't ever done this myself, but I understand that it happens regularly. At the very least, it's worth the inquiry to save a few dollars after the fact. I think you need to call the airline when you see the lower fare (I'm pretty sure that the flights have to be the same date and time as the original ones on your tickets) and they will guide you from there. It might be that they give you credit for a future flight, but that could just make the next trip even cheaper!
Good luck!
