One of my mentors taught me that the amount of information we know pales in comparison to the amount of information that we don't even know that we don't know. So ask questions, even if they feel uncomfortable. Chances are that you're not the only person who wants to know the answer. And not only will your courage create space for others to ask tough questions, you will increase the information available to help everyone move forward with whatever the issue is, since we don't know far more than we do know.
As a young woman in the workplace, by far the most important question that I learned to ask was, "Can we please turn the room temperature up by a couple of degrees?" I figured that if the room was so cold that I could hardly think, someone else in the room must be feeling cold also. Typically that "someone" turned out to be all of the women in the room, who just weren't going to say anything but were glad that I did. The men seemed to have a different metabolism. Or perhaps it was just that they were wearing suits with pants as well as socks and undershirts, and we were wearing suits with skirts or dresses and the dreaded pantyhose. I have been told that the most important question a mature women must to learn to ask is, "Can we turn the air conditioning on the highest setting possible right this very minute before I melt, dammit?" But I wouldn't know. ;)
On a more serious note, I am working on asking for help earlier. I think I have lived on my own and away from my family and as a single person and self employed for so long, by the time it occurs to me to ask for help, the S on my chest is already very sweaty.
What has been the most important question you've learned to ask? What do you need to practice asking?