IT business skill No. 1: Listening
If you have to choose just one skill to acquire or improve, make it this one. More than any other single skill, the ability to not just hear what someone else is saying, but to make sure you understand what they're trying to tell you -- regardless of whether they're explaining it well or you agree with them -- is hard to overstate.
Good listeners have an advantage over everyone else: They're constantly learning what everyone around them knows, which makes them smarter than those who are busy showing how smart they are.