If you decide to approach people to find out about their business problems, they'll take you much more seriously if you already have some knowledge of their ind

If you decide to approach people to find out about their business problems, they'll take you much more seriously if you already have some knowledge of their industry. They're not going to have confidence that you can solve (or even understand) their problems if you don't know the first thing about what they do. I'd guess that every industry has its own specialized news sites (something like TechCrunch.com, but for bankers or civil engineers). You could try finding some of these on the web and reading them. You can also learn a lot about different industries by reading a good business paper, like the WSJ or the business section of the NY Times. There are also locally oriented news sources, like Crain’s New York Business.