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1. Preselect in the Altitude window in the MCP the next hard altitude from the approach chart which should match the constraints in the FMC (this is just in case there is any constraints missing in the FMC beacuase even if you set MDA directly and the aircraft is in VNAV PATH would still comply with the contraints) then once passed the Final Approach Fix, se the MDA rounded to the nearest hundreds. Make sure your in VNAV PATH, VNAV SPEED will not comply any contraints.
2. VORLOC for Localiser only approaches, LNAV for all others.
Alex.