Just work out some "Gates" that you want to be in, and work from there.
Over time you'll learn to tidy it up a bit (I'm quite new on my current type, and so still adjusting to it too, so I know how you feel!).
The most important one that I need on the 767 is 250kts at 5000ft with 20 track miles to go. (Thats the track miles I think I'll fly, not necesarily what the FMC says). If i'm there, I know i'm set. If I'm at 6000ft, then I'm 1000ft high, and can correct that accordingly. Same goes for speed.
Others some people use are 30nm @ 8000ft and 40nm @10,000ft. After that, its a case of getting a feel for things.
Just be conservative to start with, and if its looking nasty, get the gear down
Gear solves everything.