I don't know much about PSA, but as far as interviews in general go, wear a suit and tie with dress shoes, clean shaven, (no 5 o'clock shadow) get your hair cut a day or so before, make sure your finger nails are clean, look your interviewer in the eye, firm handshake and smile.
Arrive about 10 minutes early, DON'T BE LATE!

Make sure all your paperwork is in order, neat and presentable. I take a brief case with me. Log book, resume, letters of rec, copies of license & medical all ready and neatly organized.

Airlines aren't looking for anyone particularly special, just normal. Be positive, don't talk negatively about instructing, previous employers etc.

Don't B.S. your interviewer, be honest with your answers and if you don't know the answer to a question, just be honest. Don't get too carried away with TMAAT stories. Stick to basic stuff that we have all come across.

Assume you are being watched at all times. Don't swear, rip ass, or sit there texting on your phone, even in the break room!

If for whatever reason you are not successful you will have gained valuable interview experience and almost all of the regional are hiring right now.

Good luck, let us know how you get on.