Have an idea of how many track miles your aircraft needs to descend in normal descent config (e.g. roughly 3 nm per 1000') and keep checking you're not getting high or low by checking this now and again (gross error checks) during the descent.
Set up the FMC with 'gates' - speeds and altitudes you'd like to be at at certain points. That gives VNAV the info it needs to plan a T/D etc. Plug in winds to the box to help it out and keep an eye on the actual wind during the descent and correct as necessary. When ATC step in and level you off/give you speeds etc. you'll no doubt revert to the more basic modes on the MCP (FLCH, HDG SEL etc.) - keep updating the magenta line to reflect what you're actually being asked to do as best you can and you'll have useful profile deviation info to work with. When you get close in, adjust your V/S as needed to try and achieve a continuous descent approach - use the range arc on your HSI to estimate when you'll level off at your cleared level in the MCP. Bear in mind you'll want track miles to reduce speed too (e.g. 1 nm per 10 knots).
That, or just keep the runway at the same place on the windscreen all the way down
And, obviously, ask your training captains how they do it - that's the whole point of line training!
It's a combination of all of these things in reality - you end up taking info from all the sources on the aircraft and building of picture of where you are and where you want to be. I'm relatively new to it too - sometimes it works out well, sometimes not so well. Every day's a school day!
There's usually a lot of ways to achieve the same thing - if you want to increase your ROD you can speed up or use some speedbrake - if you're close in you might prefer to use speedbrake/gear/flap etc. as increasing speed increases your energy and it's speed you'll need to lose at some point! Just an example.
B&S