I once wrote a 4000-word article on how to choose a niche on this domain but it has since been removed because the answer is really easy. Pick something you like, if you don't like anything choose something your willing to learn about if your not willing to learn well you need to go get this bit of paper called a job application and start there.
Live Life, Laugh
Have Fun, And Make New Friends. Also, check this site I run if you need free advertising ShareMyAds.com (SMA)