1/ Determine a method for knowing the track miles to run (prog page or DME or rings on the EHSI)
2/ Start your descent at 3x +10nm
3/ Constantly monitor the 3x profile and if it gets to be exactly 3x profile then use speedbrake to get back to about 3x +5.
Just do that for a month or so until you start to get a feel for the a/c then you can start to manage it a bit more efficiently.
There really are a lot of variables that you will get used to and at some stage during the flight it is going to have to come back onto a 3x profile but that is normally between 4000 and 3000ft .
eg if you are at 30,000ft start your descent at (30x3 +10) 100nm
at 25000ft you might be at say, 81nm to touch down, so you would think to yourself "a-ha! I'm at 3x plus 6 therefore I'm slowly getting higher"
If you then find yourself at 20,000ft and 60nm you could bring out the speedbrake so that at 15,000ft you are at 50nm. etc etc etc.
I know there are going to be responses to this saying "no no don't ever use your speedbrake blah blah blah" but when you are just learning I reckon it's a good tool if things are starting to get away from you.
Summary; start at 3x +10
keep it between (3x+10) and (3x+5)
at 4000ft use the slow down to bring it onto a 3x profile
