"What one thing can I do that, if I did it on a regular basis, would make a positive difference in my personal life? Meet new people."
"What one thing in my professional/business life would bring similar results? Planning/organizing"
The first answer has changed since '02. Getting out and doing things I enjoy would be my current answer. I have found that when I am having a good time I invariably meet new people. No one wants to be around a depressed or negative person.
The second answer still holds true. I fear that getting organized may prove to be a life long pursuit.