Don't know if this works for everyone, but it works for me. I usually log into Travelocity or Expedia to see what fares are showing up for the city I'm seeking to visit, and then after seeing what they are showing, dates/fares/times etc., then I swing over to the specific airline website to further investigate or book.
I've found that even when Delta shows up on Travelocity at a good fare, if you go to their site, it is even a few dollars less. Just my own experience...not saying this is always the case. This just happened for me the day before the 4th of July when I "lucked" into an excellent fare from my city to the west coast. After spotting it on Travelocity, I went over to the airlines own website and saved about $8 more on each ticket from what Travelocity was showing. Again, just my own experience.
Good luck....