For those that have successful businesses, can you explain/share tips on how you found your niche idea that people would pay you for?

There's really no formula. The best you can do is keep trying to learn things and talk to people. Drawing on your own direct experience is best, but requires some luck and creativity, too.

• professional audiences
• that you belong to
• and that gather online

Have an idea, keep asking, R&D and researching what we can improve on the products that are already in market (i.e. how can we improve on the negative comments of the product).

I successfully built an email list (CFPLand.com) around a niche because it was one I knew well and was part of (tech conference speakers).

A lot of founders use this strategy, and I think it's one of the easiest ways to find a good problem. Solve it for yourself, then listen to others with similar problems and generalize your solution.

This article may be really helpful for you :)
http://www.paulgraham.com/startupideas.html

You have to have a genuine passion for something AND be fortunate enough that there's an opportunity - something that other people who are passionate about this thing really need. It took until I reached the age of 42 to find it. I can't fake that passion.