I'm not asking you to disclose your niches, just how you chose them. Did you choose one you were interested in or one that was popular that you had no real interest in? Did you choose a small market with little competition or a huge market pretty much over saturated with competitors.
My method- Small market but very targeted with little competition. Gives me small results but fast and with less efforts (i can always multiply my results by duplicating for another small niche). Good keyword research and on page SEO is the key to my success.
Find high traffic keywords and do allintitle:keyword searches to see how many sites are targeting them. If there's more than a five hundred try longer chain keywords. Also try to find keywords that are used by people who are in the buying side of the market. For example: Don't use canon camera. Use canon eos rebel digital camera xti. I don't know if that is the right model name for the camera but you get the idea.