Before writing & wasting our brain & time, its essential to figure out what topic will hit the audience & they want to read. It is very difficult to find out new hot topics which audience want to read & they are searching it out through search engines.  Writing on useless topic or on the topics which already available on website will not give any benefits.
Now lets discuss about how to figure out topic to write.

Google has provided a site to find out the trends of people what they are searching & their interest below is the sight given :

Let me give you an advice as I am a SEO person, Just focus on "Big G" i.e. "google" . Google can give you enough traffic as compared to other

 Well I find out topic through :
(i)    Google insight in searching a topics
(ii)    I am finding current Hot news topics of country are also beneficial for writing as many of the citizens try to search it on the internet.
(iii)   When you search any thing which you want & you didn't find it easily. Then after finding it wrote an article on it.

Well Now you know why i wrote this article? Yeah true I figure out none of the site giving these essencial points so i wrote an article.

Good Luck