Just to add, using the constant descent approach method of flying the non-precision approach you must not descend below MDA, therefore you need to initiate a go-around before reaching MDA. Our SOP is to add 50' to the published MDA, bug that and make it a 'non-precision decision altitude' (if that makes sense, it's not an official name for it!)
As for the 737, when you level at the platform altitude we wind the altitude window 1000' above platform. You can then start a descent away from your present altitude in vertical speed. If the missed approach altitude is below the platform we wait until we are 1000' below the missed approach altitude and then set it. This prevents the a/c going into Alt Acq and climbing back to the MCP altitude window.
PP