I used to spend way too much time comparing different travel sites, but I finally realized that the real deals are hidden right on the Southwest homepage. Last spring, I was desperate for a cheap getaway to visit my cousins, so I started checking the "Low Fare Calendar" every Tuesday morning. I managed to snag a one-way ticket for $59 just by being flexible and shifting my flight by a single day.
Using that calendar tool is naturally the best way to spot the price dips. If you find an even lower fare later, you can always modify your booking to get the difference back!