I have a small credit with Southwest from January and I'm watching (daily!) for sale fares in July. Just wondering how I get that credited to my next flight...can I do it online or do I call?
You can do it online. When you make your reservations and get to the point of paying, they will ask if you want to apply unused credits (or something along that line), you click on that and fill in all the information they ask for.
Then it will show you a balance that you will have to pay. Very simple and once you get to that point, very self explanatory.