I fly Southwest on a regular basis and I like their open seating policy. The online check-in system eliminates the need to arrive at the airport several hours early to get a good seat.
Go to Southwest's web site (www.southwest.com) and click on Travel Center, then select "Retrieve/Email Air Reservation". Enter your confirmation number and it will display all the details of your flight(s) and verifies that you have an E-ticket instead of a printed one.
With an e-ticket, just check into the same page 24 hours before your flight leaves, click on "Check In Online / Print boarding pass" and you'll be able to print out your boarding pass. This is the document you need to get onto the plane, which means you don't have to stand in line at the airport ticket counter - you can go through security and go right to the gate. If you want to check your bags there are express lines in the ticket counter area or you can give them to the curbside skycap. Checking in 24 hours in advance virtually guarantees you'll get one of the coveted "A" boarding passes, which lets you onto the plane with the first group of passengers, right after the people who qualify for pre-boarding. If you have a condition that qualifies you for pre-boarding, you can get a pre-boarding pass at the gate when you get there.
If you can't print out your boarding pass online, you can do it using the airport kiosks, but you'll probably get a "B" or "C" boarding pass. These groups board after the "A" group, so you'll have less chance of finding two adjacent seats.
