Learn your "flows". Also, your bold face items (from memory items), checklists, every light and switch and gauge on all panels (yours, the captains, the first officers, the pedestal, and the overhead), and study your walkaround photos (if your company provides them.) The flight engineer job is a different world than actually flying the jet, as you're expected to do both your job as well as be the backup for the two guys up front. Sounds like a lot, but once you move for the purposes of flight, it's rather easy, and you can critique their landings with impunity. Just be sure to stop doing that a few months before you check out in a front seat, or someone will be on your case for your landings. When I was in the back of the Boeing 727 (for 5 years), I used to hand up a job change application form to either of the front enders if they had a bad landing. Everyone enjoyed that little treat. I got a few of them myself.