To put it simply.... patience.
You'll get noticed and a grunt will make a recommendation. Then you'll be promoted (sometimes the grunt will give you a mini quest of some sort).
I'll promote you now if you agree to go on "Thurg's survival quest".
And complete it fully.
__________________
*prays to the Giitz'Krieg*
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Wun gambul? *pulls out special dice cup*
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Yubgug: Id wuz da Boogie Oomie!
Thurg: *wets himself*