I have seen elsewhere that people say "if you can fog a mirror you are in." That is not correct. My group had 3/12 get offers, consisting of 1 FO, 1 cadet, 1 RTP (me).
After picking the brains of a couple folks, they weren't asked anything particularly hard but missed them anyway. To practice, set up a scenario from 1 airport to another, check WX and notams, practice briefing the SID, STAR, approach and ask yourself questions all along the way like the usual can I take off, do I have wx for the approach, what if wx goes to X here at the FAF, etc. That prep has gotten me through multiple military checkrides and an airline interview apparently.