Are you actually calling the airlines, looking up on their websites, or looking up the 'search' websites (travelocity, expedia, etc.).
My best experience (I do a lot of international flying out of BWI) is with actually calling the airlines. The 'search' websites tend to not do as well. If you call them, sometimes they'll tell you when specials and deals are coming. Or how you can modify your flights to get better prices. Certain days have better prices then others. Sorry, couldn't tell you what are the best days.