Your Secret Tips on how to find and choose Products to sell

Hi, for you kind hearted people who would share their secret tips, I would so much be appreciate it. I am learning some marketing, but I need the hard core secrets from the old school guys who can advise me on the secret places to go.

Please post here or email me about secret tips on how you find and choose niche products that will sell and make you a good living, and where you go to find these things, and also what makes you decide if you should choose the product for you to sell in the end?

Have a good day,
Max