For women, the biggest hidden rule is sleeping your way up, I suppose.

It's an open secret most Chinese actresses at one point or another slept with this or this director. I don't know if that's the case on a more systemic level, but I wouldn't see why it'd be so different from back home, with the exception of them not having very strict sexual harassment rules here in China.

I would be shocked if the crying secretary asked me to sleep with her! No-no-no! Same goes with the irish land whale and everybody else!

But i admit I can be partial. If one of my minion could complete the whole Westside story choreography, I'd be sure to give that employee a raise!

And of course I'd be moar enclined to give a promotion to an employee that'd greet me with a spin-o-rama high-five pelvic thrust every morning!

Grease the palms of whoever's higher than you - that goes for men
As previously stated, sleeping your way up - that's for women, at least the attractive ones.

Having the right connections is the biggest contributory factor. "Buying" positions is also a very popular method. High tolerance to alcohol can be another.

Don't try to impress your superiors by doing something better than they did and take credit. They will feel threatened and make sure you have no opportunities to advance (this was told to me by a girl working for china mobile who had to act like her good work was all because of her managers guidance so she would be able to get promoted)