Here is what you need to know. IN THIS ORDER.
1. IFR Oral guide(All questions, even those on the gouge, are from the IFR oral guide)
2. ATP Oral guide
3. FlightSim ILS 32, possibly 36 I can't remember, into INDY. Use a baron.
4. Systems
Just read through your systems. Don't spend the majority of your time there. I decided to read the IFR oral guide on my way up there was done in less than half the time of the rest of the guys. Simply because i had just read it all. They hired me on the spot. My friend with the 45hrs of multi did as I told him and they hired him as well. DO NOT BS ANYONE. Answer the question and smile. If Mrs. Bannister is not the one to do your oral don't sweat it. She'll call you within the next hour or so to let you know your hired. Just because they don't tell you on the spot doesn't mean to run off shakin up.
Everything else kilo mentioned might be good but isn't needed. Anything else needed she'll hand you a packet and you can find out by reading that thing the time you have before going in.
They did use to have a Purdue pref. hiring bit but have since cancled it. They weren't getting the results they were looking for. The purdue guys had excellent systems knowledge but overall were carrying something into the cockpit with them that a lot of the senior guys didn't like so they've since gone back to the practice of just going out and hiring people working for their hours that have a nice smile and firm handshake in the interview.