I have interviewed at two majors, two commuters, and a pilot selection board in the Air Force, and this was by far the most difficult interview of them all. The process is a two day ordeal.
Day 1 is a simulator check. You could find yourself in any sim that is open when you interview (DC10, 727, A300). It is "simply" basic airwork and ATC procedures, and the profile is divided into these two areas. First off, you do basic climbs, turns, and airspeed changes, all while holding specific vertical speeds. Sounds easy, but realize that it just so happens that everytime you are leveling off, you are also rolling out, and maybe even changing airspeeds, needless to say it can get busy. They do a good job at checking your scan, and the profile is good at pointing out weeknesses. The only real help is to have a game plan on how to utilize the 2 minute warm-up...i.e., figure out power setting for a 200 knot climb and descent (power idle works well), look at pitch to maintain 1000 fpm climb and descent, and so forth. It follows this pattern:
-Cardinal heading at 5000 ft.
-slow from 250-200
-at 200, descend do 2000 ft at 1000fpm
-during the descent, turn rt to cardinal heading at 30 deg bank
-at 2000, accel to 250 and turn left 30 bank to heading
-climb at 250 kts to 5000 ft at 1000 fpm
-turn right to heading 30 deg bank
-at 5000, turn to heading
-steep turns, 45 deg bank, specific headings they give
The next part of the sim is the ATC portion - commuter guys, this is easy. You are cleared direct a VOR, and told to expect holding clearance. They want to see that you begin slowing to appropriate speed for 5000 ft (200, be careful-stick shaker at about 190),then copy instructions and get EFC time while flying the plane and using the handheld mic. Figure your hold out and what way to enter it. You will change altitudes crossing the VOR, while reporting entering the hold and altitude. Remember to start the time and level off at right altitude. After one turn established in the hold, the eval is over.
I wish I could tell you how they grade the sim, but it is like nothing we are used to in this profession. I will say this, the people that come out of it thinking their stuff doesn't stink should be worried, those are usually the ones that have problems. The ones that come out with their tail between their legs are usually okay after a long afternoon of sweating and waiting for "THE" phone call. Don't ever get comfortable, constantly keep correcting. If you are 100 feet off fix it, if you are 5 feet off, fix it! I have talked to people that work here that say they were off 700 feet at one point during the ride (don't laugh, it could happen to you too.) Just never give up. Give them your best 30 minutes of flying you can that day, and the rest is out of your hands. Don't hold yourself to ATP standards, hold yourself to perfection (and no, my sim ride wasn't perfect.)
So, after you get the thumbs up on the sim, take a deep breath and relax, because the fun is only beginning. Day two will start at 0800, and you hit the ground running. You will go through a series of tests that I don't have the time here to explain, but if you have ever taken the AFOQT, then you know what you are in for. They are a series of timed battery type tests (I hear they are on computer now) anywhere from 3-25 minutes long each. FedEx tells you to prepare for them by taking practice standard exams like college entrance or military flight officer exams. They measure general intelligence, vocabulary, math, map reading, and reading comprehension. Really they make you feel not so smart. I was literally trying to pronounce some of the words that were ANSWERS on the vocab test. The math is easy...follow order of operations (PEMDAS...please excuse my dear aunt sandy...parenthesis, exponents, multiplication, division, addition, subtraction). I am no good at reading, so no advice there. Basically, they are looking to make sure that you are not doorknob stupid or beautiful mind smart. They supposedly gave these tests to the first 100 pilots and developed a bell curve, and they want you to fall into it. Be sure to READ the instructions before you do anything. I almost think that is part of the testing as well. They are looking to hire pilots, people who can function on a 7 day trip without driving their crewmembers crazy, enough said.
Needless to say you will be ready for lunch. Afterwards, you will either go into the 2 on 1 interview (two pilots vs. you) or into the SBI interview (situational based interview or CRM interview).
The 2 on 1 is actually not too bad. Remember, these are pilots you are with, and they are good guys. They are just trying to feel you out and get a sense of who you are and what you bring to the company. They go over your logbooks and paperwork. One person is asking you questions while the other is checking over everything. Once the questions start, both people spend most time looking down and writing, not a lot of eye contact. The questions are all of the ones you have heard before...the tell me about a time ones. Here goes nothing,

tell us about yourself since highschool
what kind of pilot are you
where did you grow up
where did you go to school
what would your friends/enemies say about you
who recommended you
what do you think about our preference for a 4 year degree
what was most stressful situation you were in
how do you handle stress
what would your spouse say about you
tell about something you couldn't make work
what are your professional and personal strenghts and weeknesses
tell about a minority situation you were in
how would you feel about flying with two females
where do you think fedex will have future problems
what is fedex's biggest obstacle to growth
what would you do if you realized someone padded their logbook
what would you look for in a pilot candidate
how do you handle stress in your family
how do you relieve stress
how do you relax
how do you stay happy
what is worst part of your current job
what would you do if you had a good idea to get it out
have you ever been grounded or grounded yourself for an emotional reason
have you ever removed yourself from the flying schedule
what would you do if CA was not following regs - breaking mins
most difficult decision you have made
why would you dismiss an employ
who would you rather work for...ups or fedex
how are you as an instructor pilot
how would you treat a new FO
how would you handle a captain you didn't like to talk to
what would you do if you lost gyros on an approach
describe an emergency you had, could you have handled it better
what kind of problem would you take to the company
" union
tell about a regular day at your airline
how do you manipulate people
what is professionalism
what was your worst decision
what was your most dumb decision
dumbest thing you have done in an airplane
what irritates you in an airplane
who do you like to associate with, what kind of people
who brings more to cockpit-fighter or heavy pilot
anything is game about your current aircraft as far as questions

Finally, off to the SBI. Here is where they want to see how you function in a timed environment working in a crew. You are the captain of a 3 member crew, and a problem arises. You have to work the problem in an orderly fashion, while keeping track of time and fuel. The big thing here is to stay focused and keep working. There is no good answer, which is why they want to see that you systematically pick one and execute it. By that I mean always work in order of most junior crewmember (SO) first, then go to the FO. You will have access to info that dispatch has and can have your SO work with them while you and the FO take care of other things. Utilize all of your resources to find your solution. Chances are the two people are not going to agree on what to do, so you ultimately make the decision - that whole PIC things creeps up again. These guys are really good at this scenario, so use them for all their worth. Don't let time slip away from you, and don't finish five minutes early. My bet is that it will go by faster than you think. Afterwards, you get to critique yourself. You will write down some things you did good and somethings you did wrong. Use CRM type words and don't hold back, they KNOW what you did good and bad.

That is the process. I hope somehow this gives you the direction you need in figuring out how to prepare. Like you have heard before, they want to hire you, and after all of the paperwork you get to do before the interview, they should! Just go into it and never give up. My head hurt when I walked out of the training center, as did most of my friends. Yet in some twisted way, it is rewarding. I had no idea how I did when it was all over. Part of me thought it went well, and part of me didn't. Then came the two hours after the interview when you are full-on second guessing everything that came out of your mouth. Don't worry about it, you probably did better than you think. They know the pressure you are under, especially in todays day and age, and they want to see you succeed. They will notify you anywhere from three to eight weeks after the interview. GOOD LUCK!