All,
Here is the cliff notes....
Be relaxed but always take the formal route. It's a job interview. You will be relaxed because you prepared, practiced and polished. I call it the 3 Ps. The people interviewing have the job and they don't have to perform but you do! They put you at ease so we can see the best in you. We are all human and I say crap more than I should. Again, it's an interview for a million dollar career. Be polite and polished. It's silly that we have pomp and circumstances but we do. All, even SWA, has this in their interview and you gotta master it. We all have great stories and experiences and you just have to express it in a logical and professional way.