Lets say you want your own fishing tackle web site,well fishing in its self is a massive niche,and with massive competition,so to start it would be better to specialise in one or two products within that niche,i have a friend that only sells floats,and another that sells hooks,and if you fish you will know that you are always buying these two products,and these two products are light,so easy to post.
So look for a niche within a niche.This web site is about working from home,but at this time there are over thirty niches on these pages all relating to working from home,for egs affiliate marketing,drop shipping,arbitrage,are niches related to working online.So pick a niche become good at it before you move on.
Ray
Work from Home - Pick a Niche