OMB, normal procedures is the bread and butter. Learn that very well.
FCOM is more for reference, you should have a good working knowledge of it, and most importantly know where to find things.
What may be obvious but nobody explicitly explained, FCOM abonormal procedures should exactly match ecam procedures.
Learn what is in the QRH.
OMC and OMD have a flick through but don't spend too much time.