MCP altitude setting for descents
 

If you are nearing the top of your descent, at some point you must dial down the altitude constraint in the MCP to allow the descent. Normally, I presume that ATC will clear you to a lower altitude, and you'll put this altitude in the MCP. But if ATC says "cleared to descend via the XXX arrival," meaning that you can follow the arrival down with the published constraints (which are presumably already programmed into your FMS), what altitude do you put in the MCP? Do you just set it to zero, or do you put it below the altitude where you expect to be when you start your ILS approach (if applicable), or what?

In my sim I'm never sure what to set it to when I'm cleared to descend via a published arrival, so usually I set it no lower than terrain between me and my destination airport, or below the altitude at which I expect to become established on the glide slope for landing. But is there a better, more coherent policy for setting the MCP altitude? Or perhaps a formal regulation/policy that says how to set it?

For example ourselves today arriveing into Alicante we followed the arrival to rwy 28. After contacticting APP we we're fully cleared the VOR/DME app to rwy 28 however all the way during the approach we x-checked the altitudes despite being fully visual. Some previous a/c we're c;eared to a straight inn 8mile final wheras we had to follow the full procedure.

If you are cleared to descend "via" a published RNAV arrival, then if you want, you can select the final platform height in the MCP.

Having done that the aircraft will attempt to make all the height and speed constraints within the RNAV STAR. You do need to remember to select QNH at the appropriate point. I put that point in the fix page, and that serves as a prompt.

I use the word attempt, because the 744 is a simple beast. You do need to watch it closely.