Ding fares are offered thru Southwest airlines. It's kind of a stock market for flights.
Download the Ding onto your computer. Once to twice a day, they offer cheaper airfares on select cities, select flights, and select dates. You can customize to give you the cities you are interested in. If you're at the computer when it comes thru, you'll hear the "ding". Otherwise you keep checking the little icon at the bottom of your puter. It will have the SW triangle logo and if there's a new message, a little letter icon is on the triangle.
So the game begins. You watch daily for the cities and dates you want to travel. For example, right now, most of the dates are in Sept. Some cities are offered only on certain days. Watch it for a few days and you'll see the patterns.
Last April, we wanted May flights and I purchased a Click n Save fare (their specials) for $59. A Ding came up for $55 but not enough for me to change. Then a $49 fare came up and I was able to change and save about $100 for our family towards a future flight (since it's not refundable).
Sorry this is long and I hope it was helpful.