To Summerrluvv: If you are at the very front of the C line, you will almost certainlly get 2 seats together. If you are worried, get to the airport early.
To Aprilgal2: SW's seating policy isn't for everybody, but it saves money, cuts delays, and is preferred by most experienced SW flyers over "normal" systems. They aren't changing it.
To Marseeya: Short answer: SW doesn't assing seats. When you get on the plane, you pick whatever seat you want. To figure out when you board the plane, they break people into 4 groups: pre-boards, A, B and C. You are assigned to the A, B and C groups depending upon when you check-in for your flight. Within each group, there is an orderly line at the airport which you can get in as soon as you arrive. For tons of talk on the SW system, check out the many threads in the Transportation forum.