Main principles or goals really help out when in game , when action is going on its really hard to think of ultimate guides and huge strategies, but when you have ONE or a few of MAIN GOALS its extremely easy to think, its not even in wc3 only , this goes to everything, lets say in survival in wilderness main principle would be setting up fire, fire is the most basic thing you will need and from it you can adapt into anything.
In wc3 main principle can always be: (with human)
Get an army which can fight
Creep , exchange combat if needed, have army which you can micro, so if you put enough effort you wont lose units, be somewhat defencive
While fighting take an expo with towers or tech to new units
3 basic rules, you will never fail with them, with any race really. Wc3 is shit simple, just win