Best tip (for RW anyway) i've read is to use the F5 display to balance the steam production and steam usage. If you keep the steam production and usage in balance, then logically you shouldn't stall. To oversimplify things horrendously, once underway there there 2 basic schools of driving:
1. full regulator, and alter the amount of power and steam consumption using the reverser (think of it as a variable gearbox). On the flat with a light load you may be down to 15%, on a really tough slow climb you may be all the way up to 65-75%
2. Combinations of regulator and and cut off e.g. 75% regulator, 25% cutoff. This is more a game of knowing the loco and watching the steam consumption - fine adjustments do make a difference. Note that many locos have 2 valves in the regulator, and 49% regulator is the first valve and over that is the second valve, with a big jump in steam usage and performance.
The other important thing is to open and close the dampers to create more steam when you need it. This seems to act as a cue to the AI fireman in some locos.
There a technical but interesting thread here on the 56XX but the principles should apply.
http://ftp.uktrainsim.com/viewtopic.php ... 0deee99c0a
Hope that helps, I struggled at first but its really a case of practice and observation. Try a flatter route to learn at first as it removes a variable.
B