I rarely need same day flights or even short notice flights unless they're for work (in which case they would book the flight for me using their travel agent). As a result I'm flexible with the airline and travel dates and usually have months in advance to shop. Typically I'll set up alerts on Hopper as soon as I know I'll be traveling, and that will tell me the right time to buy. I'll often also look at the budget airlines sites themselves as well because I know a lot of them don't allow aggregators.