In order to find a niche market, you must be able to research a market properly.
One of the ways to do this is keyword research and this is THE most important part. If you choose a very competitive keyword you will be stuck at the bottom of the search engine results, waiting for months before you get any visitors. How often do you go through every result page from a search?
On the other side, you could choose what is called a non-buying keyword, so you end up with a