I always fly Southwest and you can book and make changes fairly easily online. If the price drops, you must edit your original ticket and effectively rebook your flight. They will then take the refund and hold it for future use. You don't get an actual refund for the lowest price fares. The "refund" will be tied to your original confirmation number, so hang onto your email they send you. I have changed by schedule several times over the last month or so to take advantage of discounts, etc. I went through each of my several confirmation numbers the other day and found a total of about $125 which I applied. I was able to get my airfare from OKC to MCO down to $240 round trip minus about $75 of the refunds. (I saved some for later.)