All the psychological testing in the world isn't as good as a panel of crew assessing the person in front of them.
There's 2 questions that they think.
1. Can I trust this guy to fly my Mother or Partner?
and
2. Can I sit in a cockpit for 8+ hours without wanting to strangle him/her?
You might think that they are flippant questions. They most certainly are not. First one assesses their technical competence backed up with a sim report and the second question assesses their personality.
Some may think that the sim ride assesses only your IR skills. Not true, your experience is noted and nerves are taken into account. If you can't ask for flaps or gear without appearing snappy and harrassed then your suitability will come under question.
So my advice. Be the best pilot you can be. Study as much as possible but also show genuine interest in aviation. Pop along to an airshow or two. It's handy to be able to recognise different fleets and if nothing else, just enjoy aviation.
If you're not a naturally social sort of person, learn. Join a tennis group, play social soccer or go rambling. Whatever it takes to get you to interact with different people on a social level. This skill is imperative, esp as a new FO.
Oh I forgot. At the interview, switch off your phone and wear a suit.
Good luck.