1) If you are conducting an ILS and you pass the FAF above the published altitude, you need to add that altitude to the DA.
2) If at the FAF the altimeter underreads then you use the same DA. (JEPP TERMINAL Instrument Approach/takeoff 2.7.3.1, states any unexplained descrepancy, then conduct a MA)
This used to be the rule in Australia quite a few years ago but was never a part of the ICAO docs as far as I know. It has been replaced with the requirement for a missed approach in line with ICAO.
3)If you are more than half scale deflection you conduct a missed approach. (Jepp Instr app/takeoff procedures 2.7.3.1, states anytime the LOC or GS indicates full scale deflection a MA SHOULD be conducted)
From the AIP/Jepp terminal:
"A missed approach must be executed if:
a. during the final segment of an instrument approach, the aircraft
is not maintained within the applicable navigation tolerance for
the aid in use"
4) If you have a raim warning below the MSA you may continue at that altitude to the MAP. ( I think this is an old rule, as JEPP DGA procedures, 1.5.1.f states if there is a raim warning or any doubt off the gps information, a MA must be conducted)
Sounds like a more practical interpretation of the rules than a technically correct one. I guess in theory if you've descended to your current altitude with RAIM available and then it drops out, the altitude you're at is definitely still safe because you got there using valid distance information. The steps always get lower on a DGA so your current altitude would continue to be safe until you reach the missed approach point.