Have the balls to stand up to management. You are often under significant pressure to adjust timelines and somehow get "9 women to have a baby in a month."
The PM I have now is excellent and is happy to say things to management like:
"Assuming everything goes well, we estimate you will have your project on dd-mm-yy. Remember that's an ESTIMATE."
"I don't think it's a good idea to try and force our devs to work overtime/weekends. We're more likely to stress our workforce and possibly lose devs eventually if we do that."
"No I'm not changing my estimate."
"No really, I'm not changing my estimate."
You get the idea. Thing is, after a number of projects he actually has the respect of management because they know he will give them the real numbers no matter what the pressure.