Look into the fleets and the future plans for the fleets (getting rid of the 145?)
Know about the aircraft you are starting on eg the Q400's NVS
Look into the green policies
Generally the flybe website is one of the best sources of information
There tends to be a technical question, nothing too hard normally and if there is a white board in the room they don't seem to mind you drawing related diagrams.
Be ready for silly questions such as
"Why not BA?" it's hard to avoid silly answers such as "Because they didn't get back to me..." but coming back to why you want flybe as an employer seems to work
All the best