The normal practice for Southwest is to pay $20 ahead of time for the group "A" seating....it must be done more than 24 hours from the scheduled flight time. Now they allow you to get group "A" seating within 24 hours if for $40.
https://www.usatoday.com/story/travel/flights/2013/01/21/southwest-40-dollars-board-first/1853667/
In other words, you better be johnny-on-the-spot when you do normal checkin and do it exactly 24 hours before the scheduled departure or you will very likely end up in a middle seat.
https://www.usatoday.com/story/travel/flights/2013/01/21/southwest-40-dollars-board-first/1853667/
In other words, you better be johnny-on-the-spot when you do normal checkin and do it exactly 24 hours before the scheduled departure or you will very likely end up in a middle seat.