Selection as already mentioned. Biggest thing is how will you adjust to the lifestyle change (assuming you aren't a night-freight dog already). You either love it or hate it. I hated it. In my opinion it is worse than a longhaul lifestyle as ALL your flying is at night and you will spend more hours hanging around dingy crew rooms (portacabins) than actually flying and that was more tedious and tiring at 3am than any flight I have ever done!
They obviosly have a retention problem due to it not being everyone's cup of tea, so they will need to hear good, well thought out reasoning about how you will fit in, how you will cope if you have family and how you will STAY. Unless things have changed since I was there you only get about 300hrs flying a year, but many, many more duty hours.
On the plus side, they are a decent employer, the hotels were mostly very good and they always paid on time....
Enjoy.
PP